ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT
AZOJETE March 2020. Vol. 16(1):85-91

Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria.
Print ISSN: 1596-2490, Electronic ISSN: 2545-5818

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ORIGINAL RESEARCH ARTICLE

KINETICS OF ANAEROBIC CO-DIGESTION OF PAUNCH MANURE AND SUGARCANE
PEELS USING COW DUNG AS INOCULUM

N. H. Abdulhakeem and A. A. Lawal
(1Department of Agricultural Technology, Federal College of Horticulture Dadin-kowa, Gombe State, Nigeria.

2Department of Agricultural and Environmental Resources Engineering, University of Maiduguri, Borno State Nigeria)
*Corresponding author’s email address: hnuruddeen15@gmail.com

1.0 Introduction
As the world population increases, so also the demand for fossil-based fuels. This demand is
further aggravated by urbanization and its attendant effects on energy demand as well as
uncertainty in fuel supply and prices in the global market (Bentley, 2002; Cavallo, 2003).
Nigeria loses an estimated five billion (USD) annually to poor environmental management
practices from environmental pollution, waste mismanagement and improper agricultural waste
handling (Melford, 2003). The resulting output of poor environment management practices
leads to pollution of air, water and environment. Exposure to these pollutants pose great threat
to human health, economic development and environmental safety. Due to these challenges,
researchers have tried to find alternative use of these Slaughterhouse wastes that includes horns,
bones, paunch manure, spent-water to transform them into a sustainable and renewable energy
source (Ezeoha and Idike, 2007; Monch-Tegeder et al., 2013; Ojolo et al., 2007).

ARTICLE INFORMATION ABSTRACT

Anaerobic co-digestion offers a prospective medium for transforming
organic solid wastes into fuel, thereby providing an extra source of
energy. This study investigates the kinetics of anaerobic co-digestion of
paunch manure and sugarcane peels using cow dung as inoculum for
biogas production. Anaerobic assay setup was in 3 digesters of 4
replicates with a total of 12 replicate batch digesters under mesophilic
temperature range (30-35°C) for a retention time of 30 days.
Cumulative biogas production for all digesters were measured and
fitted to some selected models. The modified Gompertz equation was
tested for its fitness. The kinetic parameters viz., biogas yield potential
(P), maximum biogas production rate (Rm) and the duration of lag
phase (λ) were recorded for each case as the digester with 0g sugarcane
peels (control) produced maximum biogas of (83.14 (mL/g VS)) and the
kinetic parameters P, Rm and λ were 89.0018 ml (g VS-1), 4.7089 ml (g
VS d)-1, 0.8734 days respectively. It was observed that biogas
production potential was inversely proportional to the substrate
concentration of sugarcane peels in the digesters, the highest
concentration of sugarcane peels (1.8g SP) recorded the lowest quantity
of biogas with 37.9075 mL/g VS, 1.4547 g VS-1, 1.0891 days. Therefore,
sugarcane peels should be co-digested with other substrates. The
experimental kinetic data in-line with the Gompertz Model, Modified
Gompertz Model Equation.

© 2020 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved.

Submitted 20 September, 2019
Revised 06 December, 2019
Accepted 08 January, 2020

Keywords:
anaerobic digestion
paunch manure
sugarcane peels
inoculum
modified gompertz
equation.

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Abdulhakeem and Lawal: Kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung
as inoculum. AZOJETE,16(1):85-91. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: hnuruddeen15@gmail.com 86

Some researchers argued that, the biogas production potential of paunch manure without co-
digestion results in lower biogas yields due to its composition and opined that, paunch manure
be co-digested with other substrates during the production process (Ezeoha and Idike, 2007;
Melford, 2003; Monch-Tegeder et al., 2013).
Anaerobic co-digestion is a systematic means of having more than one substrate in a formation
to form a unit for producing biogas with the aim of improving the biogas yield potential
(Jagadish et al., 2012), also as an alternative way of converting these wastes to energy, which is
cost-effective where the end products could be used as organic manure for agricultural
purposes (Bentley, 2002; Cavallo, 2003). Sugarcane peels (SP) are waste products of sugarcane
(suaccherum species) as a result of human consumption of raw sugarcane or as waste product
in jaggery production. Sugarcane is one of the major crops cultivated in Northern region of
Nigeria popularly known as “Rake” and the peels as “Bawon rake” in the local dialect.
It is noteworthy that because SP waste products are not properly utilized, it would be a good
idea to assessed its potentials as alternative source of energy. Therefore, this study intends to
investigate the kinetics of producing biomethane from slaughterhouse paunch manure (PM) co-
digested with sugarcane peels at different mixture ratios for anaerobic digestion using cow
dung as inoculum.

2.0 Materials and methods
2.1 Substrate sources and Characteristics
Fresh samples of paunch manure, sugarcane peels and inoculum were obtained sealed to avoid
moisture depletion from kasuwan shanu, Mairi ward and University of Maiduguri Animal farm in
Borno state. The samples were sun dried for 48 hours to remove excess moisture before analysis
on ash content, moisture content, total solids, volatile solids and pH.

Anaerobic Assay Set Up
Three sets of 473 ml capacity bottles were used as digesters and labelled as A, B and C with
each letter having 4 replicates of 3g of paunch manure (PM), 0, 0.6, 1.2 and 1.8g of sugarcane
peels (SP) to obtain digesters with 0%, 20%, 40% and 60% co-digestion with total of 12 digester
replicates.

Preparation of Fermentation slurries
The PM and SP used in this experiment were pulverized into about 2mm size then sun dried for
48 hours. A moisture free PM and SP were used to prepare the fermentation slurries into 0%,
20%, 40% and 60% co-digestion, 100 ml of water was added to each digester with 1 ml of stock
solution and 50 ml of inoculum. A blank assay for inoculum (Control) was used to measure the
inoculum activity in 3 replicates as in Srinidhi et al. (2012).
The digesters were set up in control temperature range of 30-35o C then allowed to undergo
anaerobic digestion for a retention time of 30 days’ mesophilic temperature range. The gas
collection was done using liquid displacement method over a 24-hour interval to measure
Cumulative biogas production (Jagadish et al., 2012).

Analytical methods
Solid analysis: Total solids (TS) and volatile solids (VS) analysis were performed for PM and SP
according to standard methods (Sluiter et al., 2008; Lay et al., 1998).

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Arid Zone Journal of Engineering, Technology and Environment, March, 2020; Vol. 16(1) 85-91. ISSN 1596-2490;
e-ISSN 2545-5818; www.azojete.com.ng

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Modified Gompertz Model
The kinetic data obtained from the study were checked using modified Gompertz model for
fitness. The equation gives the cumulative biogas production from the digesters with
assumption that the gas produced is a function of bacterial growth (Jagadish et al., 2012;
Luengo and Alvarez, 1988; Atlas, 2008).
M = P ∗ exp { − exp Rm∗e

P
λ − t + 1 } (1)

y = A exp − exp b − ct (2)
where:
M = cumulative biogas production, l/g(Vs) at any time t
P = Biogas yield potential, l/g (Vs)
Rm = Maximum biogas production rate, l/ (g VS d)
λ = Duration of lag phase, d (days)
t = time at which cumulative biogas production M is calculated, d
y = biogas production accumulation (L kg-1) at time t
t = time (day) over the digestion period.
A = biogas production potential (L kg-1)
c = constant (d-1), b= constant (no unit)
the parameters P, Rm and λ were estimated for each of the digesters using Microsoft Excel
software. These parameters were determined for best fit.

3.0 Results and discussions
3.1 Physic-chemical properties of Paunch manure and Sugarcane peels
Table 1 showed the physic-chemical properties of PM and SP. The results showed that, PM
appeared to have the same TS as SP with 80 %. The VS of SP was 88.14 % because of its organic
matter contents which was higher than that of PM with 67.78 %. The ash content for PM was
14.95 % higher than SP with 12.42 %, this is because PM contains more nonorganic nutrients as
compared to sugarcane peels which is in line with Ojolo et al., (2007). The pH values were lower
than 6.5 which inhibit the formation of acetic, lactic and propionic acids which becomes toxic for
methane forming bacteria and are essential for acetogenesis and methanogenesis. The
optimum pH for biogas production was between 7 and 8 similar to the findings of Budiyono et
al., (2013), who investigated the effect of pH on food wastes and on Buffalo manure. Moisture
content shows the percentage of liquids to solids constituents of the materials, higher liquid
contents aids in increased biogas production through increased contact between
microorganisms and organic matter as observed by Alnakeeb et al., (2017), PM and SP had
6.39% and 4.17% solids and 93.61%, 95.83% liquids.

Table 1: The Physic-chemical properties of paunch manure and sugarcane peels
Materials Total solids

(%)
Volatile
solids (%)

Moisture
content (%)

pH Ash content (%)

PM 80 67.78 6.39 7.4 14.95
SP 80 88.14 4.17 7.4 12.42

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Abdulhakeem and Lawal: Kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung
as inoculum. AZOJETE,16(1):85-91. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: hnuruddeen15@gmail.com 88

3.2 Simulation of Biogas Production Accumulation
Figure 1 shows the biogas accumulation of PM co-digested with SP, Control over a thirty-days
retention time. It was observed that the digesters (Control, SP 0.6g, SP 1.2g SP 1.8g) had 83.14
mL/g, 49.83 mL/g, 46.45 mL/g, and 30.89 mL/g respectively. This shows that as the
concentration of SP is increased in the co-digestion process with PM the production
accumulation decreases.

Figure 1: The biogas production accumulation of PM CD 0.6 g SP, 1.2 g SP and 1.8 g SP

Figure 2 shows the plot of Gompertz Model equation for the digesters; Control, PM co-digested
with 0.6g, 1.2g, and 1.8g SP. From the graph it is clear that the experimental data fits well with
the Gompertz model equation and the values for R2 were 0.98, 0.95, 0.99 and 0.99 for the
control, 0.6g SP, 1.2g SP and 1.8g SP respectively.

Figure 2: shows the plot of Gompetz Model Equation for control, PM CD with 0.6g, 1.2g and
1.8g SP

Observations made from Table 2 shows that the cumulative biogas production from each
digester was tested for fitness with the Modified Gompertz Model equation, the equation
described the cumulative biogas production with the time of digestion through biogas yield
potential (P), maximum biogas production rate(Rm) and duration of lag phase (λ). The
parameters obtained shows that the digesters Control and PM CD with 1.8 g SP had the shorter
lag period of 0.873588 days and 1.089084 days respectively while PM CD with 1.2 g SP has the
highest lag period of 4.168447 days followed by PM co-digested with 0.6g SP with 4.021884
days. Control has the maximum biogas production rate of 4.708995383 mL/ g VS then 0.6g SP
with 3.070026891 mL/ g VS, 1.2g SP was 2.251043986 mL/ g VS and 1.8g SP with 1.4546893 mL/

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Arid Zone Journal of Engineering, Technology and Environment, March, 2020; Vol. 16(1) 85-91. ISSN 1596-2490;
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g VS. The maximum biogas produced at the end of the digestion period was highest for Control
which as 89.00184625 mL/ g VS. This could be because Paunch manure is rich in nutrients and
contains adequate amount of carbon, oxygen, hydrogen, nitrogen, phosphorus, potassium,
calcium, magnesium and a number of trace elements which are very essential elements for the
growth of anaerobic bacterium as in Kanwass and Kalia, (1992). It also could have optimized
syntrophic (cross feeding) interaction between acetogenes and methanogens which is the most
critical step in the biomethanation process as reported by Schink and Stams, (2005).
Furthermore, the digesters; control, PM co-digested with 0.6g, 1.2g and 1.8g SP produced 83.14
mL/ g VS, 49.83 mL/g VS, 46.45 mL/g VS, 30.89 ml/ g VS respectively. Figure 3 shows The
experimental kinetic data fits well with the Modified Gompertz Equation.

Table 2: shows the summary of the results obtained from the Modified Gompertz model
Equation to check the performance of the digesters.
Digesters Biogas yield

(mL/ g VS)
Modified Gompertz parameters (model) R2
P, (mL/g VS) Rm (mL/g VS d) λ, d

Control 83.138 89.0018 4.7089 0.8734 0.91

0.6 g SP 49.834 54.6859 3.0700 4.02198 0.98
1.2 g SP 46.446 60.5884 2.2510 4.1684 0.72
1.8 g SP 30.889 37.9075 1.4547 1.0891 0.68

Figure 3: shows the plot of Modified Gopertz.Model Equation for the digesters control,PM CD
with 0.6g , 1.2g and 1.8g SP.

4.0 Conclusions
The conclusions drawn from this study were:
Sugarcane peels had higher volatile solids when compared to paunch manure indicating a
higher biogas potential.
It was observed that, the digester(control) produced the highest biogas with better production
rate as compared to when co-digested with varying substrate concentrations of SP.
Higher substrate concentration of SP was found to be very poor when co-digested with PM as
the digester with 1.8g SP recorded the lowest biogas production over 30 days’ retention period.

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Abdulhakeem and Lawal: Kinetics of anaerobic co-digestion of paunch manure and sugarcane peels using cow dung
as inoculum. AZOJETE,16(1):85-91. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: hnuruddeen15@gmail.com 90

SP should be co-digested with other organic wastes to investigate further alternatives to its
biogas potentials.
The simulation results indicated that the First Order Exponential Rise, Gompertz and Modified
Gompertz Model Equations best predicted the Cumulative Biogas Produced as a function of
retention time.

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e-ISSN 2545-5818; www.azojete.com.ng

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