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9 

 

 

 

Review 

An extensive examination of the potential of waste 

cooking oil biodiesel in Bangladesh 
Ahad Bin Azad, Priyam Chakraborty, Fahim Hossain, Tahmidur Rahman Siam, 
Nure Alam Siddiki* 

Department of Mechanical Engineering, Chittagong University of Engineering & Technology, Bangladesh 

A R T I C L E   I N F O 
 

Article history: 
Received 11 June 2025  
Received in revised form 
20 July 2025 
Accepted 03 September 2025 
 
Keywords: 
Biodiesel, Sustainability, Emission, Esterification 
 
*Corresponding author 
Email address:  
nurealamsiddiki456@gmail.com 
  
 
DOI: 10.55670/fpll.fuen.4.4.2 

A B S T R A C T 
 

Waste cooking oil (WCO) has gained attention as a valuable resource for 
biodiesel production due to its availability and potential for waste management. 
This study examines the viability of WCO as a biodiesel feedstock in Bangladesh, 
addressing the increasing demand for sustainable energy alternatives. This 
paper explores multiple facets of WCO biodiesel, encompassing feedstock types, 
pretreatment techniques, and the production process. The study analyzes the 
physicochemical properties, emission characteristics, performance, and 
combustion behavior of biodiesel derived from WCO. The findings indicate that 
WCO biodiesel presents considerable potential as an economically viable and 
environmentally sustainable alternative fuel for diesel engines in Bangladesh. 
Challenges in WCO collection, commercialization, and public awareness must 
be addressed to realize its full potential. The paper concludes by proposing 
avenues for further research in Bangladesh, emphasizing the enhancement of 
collection systems, the refinement of policy frameworks, and the optimization 
of conversion technologies to facilitate the broader adoption of WCO biodiesel. 
 

 
1. Introduction  

The rapid industrialization and urbanization that have 
occurred since the mid-20th century have driven the global 
surge in diesel production, providing the backbone for 
transportation, energy generation, and industrial operations 
[1]. Although diesel has played a crucial role as a fuel source, 
its associated environmental and economic issues, such as 
greenhouse gas emissions, pollution, and resource depletion, 
have ignited a global quest for sustainable alternatives. 
Carbon dioxide (CO₂) is the primary contributor to global 
warming, increasing from roughly 3.34 million tons in 1970 
to around 124.79 million tons in 2023. In 2022, global energy-
related CO₂ emissions totaled approximately 36.8 gigatons, 
representing a 0.9% increase from the previous year. In 2022, 
the transportation sector contributed nearly eight gigatons of 
CO₂ emissions, representing approximately 23% of global 
energy-related CO₂ emissions [2]. The ongoing dependence 
on fossil fuels, particularly diesel, has intensified 
environmental degradation through air pollution and climate 
change, while also raising concerns about resource depletion 
and energy security. Crude oil reserves are expected to be 
depleted by 2052, given the current annual consumption rate 
of 4 billion tons [3]. This projection indicates a looming 
energy crisis if alternative solutions are not adopted 
promptly. Bangladesh's energy sector is heavily reliant on 
fossil fuels, with more than 85% of electricity generation 
coming from conventional sources, predominantly natural 

gas, which accounts for over 50% of annual electricity 
production [4]. Even with a rise in electricity generation to 
support industrial expansion, the nation faces challenges 
stemming from dwindling fossil fuel reserves and insufficient 
oil resources, necessitating expensive imports [5]. The rising 
global fuel prices, geopolitical conflicts, and supply chain 
disruptions further strain Bangladesh’s energy security, 
prompting efforts to explore alternative energy solutions. 
Additionally, the country’s rapid industrialization and 
urbanization have led to a surge in CO₂ emissions, with fossil 
fuel combustion contributing significantly to environmental 
degradation. Bangladesh’s per capita CO₂ emissions have 
risen from approximately 0 tons in 1946 to 0.7 tons in 2023 
[6]. In 2021, fuel combustion resulted in the emission of 17.17 
million tons of CO₂, positioning Bangladesh as the 13th 
highest emitter in the Asia-Pacific region in terms of carbon 
emissions [7]. Despite accounting for only 0.09% of global 
carbon emissions, Bangladesh is significantly vulnerable to 
climate change, ranking eighth on the 2021 Global Climate 
Risk Index [8]. The government has pledged to reduce 
emissions by 21.8% by 2030, in line with the Paris 
Agreement, underscoring the urgent need for a transition to 
renewable energy sources [9]. The currently available 
number of renewables, particularly solar energy, hovers 
between 2-4%, highlighting the necessity for legislative 
reforms, financial incentives, and technological 
improvements to minimize reliance on fossil fuels and foster 

 

 

Future Energy 

Open Access Journal 

https://doi.org/10.55670/fpll.fuen.4.4.2 

 

 

November 2025| Volume 04 | Issue 04 | Pages 09-21 

Journal homepage: https://fupubco.com/fuen 

 
ISSN 2832-0328 

mailto:nurealamsiddiki456@gmail.com
https://doi.org/10.55670/fpll.fuen.4.4.2
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Ahad Bin Azad et al. /Future Energy                                                                                    November 2025| Volume 04 | Issue 04| Pages 09-21 

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sustainable energy alternatives [10].  Facing the threat of 
declining fossil fuel reserves and potential energy crises, 
nations worldwide are increasingly exploring a variety of 
alternative energy sources [11].  Bioethanol, biomethanol, 
biobutanol, biogas, and biodiesel have emerged as promising 
alternatives to fossil fuels, offering renewable and 
environmentally friendly energy sources. Bioethanol, sourced 
from agricultural feedstocks, demonstrates energy balance 
and enhances combustion efficiency; however, it is notably 
corrosive and necessitates modifications to engines [12]. 
Biomethanol, recognized for its biodegradability and 
compatibility with the current petrol distribution 
infrastructure, encounters obstacles stemming from its 
toxicity and the necessity for elevated temperature 
conditions [13]. Biobutanol, a multifaceted biofuel, can be 
utilized directly in gasoline engines without necessitating 
modifications. It offers a high energy content; however, its 
production is challenging, and it has a reduced heating value 
compared to gasoline [14]. Biogas, produced from plant and 
animal waste, is a cost-effective and sustainable fuel that 
reduces greenhouse gas emissions, yet its high impurity 
content necessitates additional refining processes [15]. 
Biodiesel, currently the most widely recognized alternative, is 
recognized for its low sulfur emissions, non-toxic 
characteristics, and ability to reduce particulate matter in 
diesel engines. Nonetheless, it presents certain challenges, 
such as heightened viscosity, which affects the efficiency of 
fuel injection. Despite showing great promise in addressing 
energy security and sustainability challenges, their inherent 
limitations necessitate further technological advancements to 
enable large-scale adoption.  

Biodiesel production continues to grow worldwide, with 
Europe leading both output (34%) and consumption (35%). 
However, raw feedstock costs—constituting up to 80% of 
total production expenses—remain a significant barrier [16]. 
Since approximately 95% of the world’s biodiesel relies on 
edible oils, the resulting increase in raw material prices has 
made biodiesel 1.5 to 2 times more expensive than diesel [17]. 
This escalation hinders commercial viability and spurs 
interest in alternative feedstocks such as non-edible oils and 
waste cooking oil (WCO), which can potentially lower 
production costs by up to 70% [18]. In Bangladesh, where an 
estimated 1-1.2 lakh tons of WCO is generated annually, only 
a small fraction is properly managed; the majority is black-
marketed or reused in restaurants, contrary to the country’s 
Food Safety Act [19]. Such practices pose serious health and 
environmental risks, yet the abundance of WCO presents a 
cost-effective option for biodiesel production, especially amid 
rising edible oil prices [20]. Recent efforts by local and 
international companies to collect and convert WCO into 
biodiesel underscore its promise as an advanced biofuel 
feedstock, highlighting the potential for both environmental 
and economic benefits. Hence, the focus of this paper is to 
examine WCO-based biodiesel within the Bangladeshi context 
and explore strategies for its sustainable large-scale 
implementation. 

2. Biodiesel and its feedstock 

Biodiesel is a renewable alternative fuel produced 
through transesterification, where oils or fats react with 
alcohol (usually methanol) in the presence of a catalyst to 
form fatty acid methyl esters (FAME), which are biodiesel 
[21]. The advantages of biodiesel include its biodegradability, 
non-explosiveness, non-flammability, and non-toxicity, 
alongside the crucial benefit of being renewable [22]. The 
feedstocks for biodiesel can be categorized into four 

generations, shown in Figure 1, with each offering distinct 
benefits and challenges.   

 
Figure 1. Generation of biodiesel feedstock 

2.1 First-generation feedstocks (1G) 
First-generation feedstocks include edible oils like palm 

oil, soybean oil, sunflower oil, and rapeseed oil, which are 
commonly used for biodiesel production due to their high oil 
content and availability [23]. However, their use has led to the 
"food vs. fuel" debate, as they compete with food crops, 
raising the cost of biodiesel production.  

2.2 Second-generation feedstock (2G) 
Second-generation feedstocks, such as Jatropha, Jojoba, 

Neem, and Waste Cooking Oil (WCO) are derived from non-
edible oils that do not compete with food production [24]. 
While these oils help mitigate the food vs. fuel issue, their 
cultivation still requires significant land, which could 
otherwise be used for food crops [25]. However, some non-
edible oils, like Jatropha, can be grown on marginal lands, 
reducing the pressure on arable land [26]. WCO, in particular, 
reduces biodiesel production costs by up to 70–80% and 
prevents environmental pollution [27]. However, WCO 
requires pretreatment due to its high impurity content [28]. 

2.3 Third-generation feedstock (3G) 
Third-generation feedstocks, such as microalgae and 

animal fats, offer significant potential for biodiesel production 
due to their low cost and availability [29]. Microalgae, with 
high lipid content and rapid growth, also hold promise but 
face challenges in large-scale cultivation due to high nutrient 
demands and land requirements.  

2.4 Fourth-generation feedstock (4G)  
Fourth-generation feedstocks, such as electro-fuels and 

solar fuels, are an emerging area of research in biodiesel 
production [30]. These feedstocks offer the potential for high 
lipid content and superior CO2 absorption, contributing to 
sustainability. However, they are still in the early stages of 
development, and the main challenge lies in making their 
production economically viable at a large scale [31]. 

3. Waste cooking oil (WCO) production 

Waste cooking oil (WCO) is produced from repeatedly 
used edible oils, which increases impurities such as free fatty 
acids (FFAs) and water, necessitating pretreatment before 
biodiesel production [32]. Globally, large quantities of WCO—
running into millions of tons—underscore its potential as a 
cheap, non-food feedstock [33]. In Bangladesh, annual edible 
oil consumption exceeds 20 lakh tons, with discarded oil often 



Ahad Bin Azad et al. /Future Energy                                                                                    November 2025| Volume 04 | Issue 04| Pages 09-21 

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reused or disposed of improperly, posing health and 
environmental threats [34]. Converting WCO into biodiesel 
can significantly cut production costs, avert reintroduction 
into the food chain, and reduce waste. Companies like 
Muenzer Bangla exemplify this potential by collecting WCO 
from restaurants and transforming it into cleaner energy, 
marking a promising path toward sustainable fuel solutions 
in Bangladesh [35].  

4. Pretreatment of WCO 

Removing impurities, free fatty acids (FFA), and water 
from waste cooking oil (WCO) is crucial for efficient biodiesel 
production [36]. High FFA can cause saponification, lowering 
biodiesel yield and increasing catalyst consumption. Common 
techniques include acid esterification with methanol and 
sulfuric acid, neutralization with alkalis, and heating above 
100 °C or vacuum distillation to eliminate water. Additionally, 
filtration and centrifugation help remove solids and 
phospholipids.   

5. Biodiesel production from WCO 

Biodiesel can be produced from waste cooking oil (WCO) 
using several distinct processes, including gasification, 
catalytic pyrolysis, hydrocracking [37], and fast pyrolysis 
[38]. Having said that, transesterification is the most widely 
used and practical method due to its effectiveness and low 
cost. One of the key benefits of biodiesel is its ability to be 
blended with conventional diesel in different ratios, such as 
B5 (5% biodiesel and 95% diesel) or B20 (20% biodiesel and 
80% diesel), making it a viable alternative for fueling internal 
combustion engines [39]. Biodiesel has approximately 9% 
less energy content than conventional diesel [40]; yet, it is 
frequently preferred for its enhanced combustion 
characteristics and significantly reduced emissions, making it 
an ecologically sustainable option.  

5.1 Transesterification 
The transesterification, also known as methanolysis, 

process involves reacting triglycerides (fats and oils) with 
alcohol (usually methanol) in the presence of a catalyst to 
produce biodiesel (fatty acid methyl esters, FAMEs) and 
glycerol as by-products [41].  

 

Figure 3. General transesterification reaction 

 

This method is preferred for large-scale biodiesel 
production because it requires minimal modifications to 
diesel engines and integrates easily into existing industrial 
systems. The process occurs in three consecutive reversible 
reactions: triglycerides are first converted to diglycerides, 
then to monoglycerides, and finally to glycerol, with each step 
producing an ester. This results in three ester molecules from 
one triglyceride [42]. When methanol is used, the product is 
methyl esters (FAMEs), while ethanol produces ethyl esters 
(FAEEs). The reaction is typically catalyzed by inorganic 
catalysts like KOH or NaOH, which accelerate the process and 
improve the yield. The general chemical equation for this 
reaction is shown in Figure 2 and Figure 3. 

 
Figure 2. Flow diagram of biodiesel production from WCO 

 

 

 

 

 



Ahad Bin Azad et al. /Future Energy                                                                                    November 2025| Volume 04 | Issue 04| Pages 09-21 

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6. Physicochemical properties of WCO 

WCO–based biodiesel exhibits several key 
physicochemical properties that impact its suitability for 
compression ignition engines. These properties are 
influenced by free fatty acid content, production methods 
(e.g., transesterification conditions), and purification steps 
[43]. Below is a brief overview of major properties—namely, 
kinematic viscosity, density, cetane number, flash point, cloud 
point, pour point, acid value, and higher heating value—as 
gleaned from the literature. Table 1 presents a comparative 
analysis of the physicochemical properties of WCO, as 
reported by various authors. 

6.1 Density 
Density plays a pivotal role in injection mass flow. WCO 

biodiesel generally has a higher density than petro-diesel. 
This is attributed to the presence of saturated and 
unsaturated fatty acids [44]. Overly high densities (e.g., >880 
kg/m³) may increase brake-specific fuel consumption, while 
blending with diesel or removing impurities can mitigate this 
issue [45]. 

6.2 Kinematic viscosity 
Kinematic viscosity critically affects fuel injection, spray 

atomization, and overall combustion efficiency. WCO 
biodiesel often displays higher viscosity than mineral diesel 
[32]. If viscosity is excessive, larger fuel droplets form, leading 
to incomplete combustion and potential deposit buildup. 
However, viscosity that is too low can reduce lubricity and 
harm the injection system. Most studies report that properly 
produced WCO biodiesel falls between 4–5 mm²/s at 40 °C, in 
line with ASTM D445 standards [45]. EN ISO 3104 (3.5 mm²/s 
to 5.0 mm²/s) and ASTM D445 (1.9 mm²/s to 6.0 mm²/s) are 
employed to assess the viscosity of biodiesel [46].  

6.3 Pour point 
Pour point is the lowest temperature at which the fuel 

remains pourable. High pour points are common in WCO 
biodiesel, especially if the source oil contains elevated 
saturated fat content (e.g., palm-derived WCO) [47]. This 
property can pose challenges in colder climates [48]. Typical 
improvement strategies include blending with lower-
viscosity fuels or adding pour-point depressants [49]. 

6.4 Flash point 
Flash point indicates the temperature at which fuel 

vapors ignite [50]. WCO biodiesel typically exhibits a higher 
flash point than diesel [51], enhancing transport and storage 
safety. Yet residual alcohol from transesterification can 
reduce flash points below the ASTM minimum (100 °C), 
emphasizing the need for thorough processing [52]. 

6.5 Cloud point 
The cloud point is the temperature at which wax crystals 

emerge, posing potential blockages in filters or injectors 
under cold conditions [45]. Due to the presence of saturated 
fatty acids, many WCO biodiesels do not meet the ASTM-
recommended sub-zero cloud point [44].  

6.6 Iodine number 
Iodine number signifies the degree of unsaturation in the 

fatty acid chains constituting biodiesel. A higher iodine 
number implies more double bonds, which can influence 
oxidative stability and cold-flow behavior [53]. WCO 
feedstocks that contain greater amounts of unsaturated fatty 
acids tend to produce biodiesel with elevated iodine numbers 
[54].  

 

6.7 Cetane number 
The cetane number measures ignition quality; higher 

values translate into shorter ignition delays and improved 
cold starting [55]. Most WCO biodiesel samples exhibit cetane 
numbers of≥47 [44], which meet the ASTM D6751 guidelines. 

6.8 Higher Heating Value (HHV) 
The higher heating value represents the total energy 

content of the fuel. WCO biodiesel typically shows an HHV 
around 39 MJ/kg, slightly lower than petroleum diesel (~43 
MJ/kg) [56]. Consequently, engines may consume a 
marginally greater volume of WCO biodiesel for the same 
power output, though the difference is often acceptable for 
most CI applications. 

6.9 Acid value 
Acid value reflects free fatty acids and oxidation 

byproducts [57]. Exceeding ~0.5 mg KOH/g can promote 
corrosive effects and fuel instability [58]. Pre-treatment steps 
such as esterification and subsequent purification are 
therefore crucial to bring acid values within ASTM limits [59].  

7. Types of catalysts 

Catalysts are essential for enhancing the 
transesterification process, playing a key role in determining 
the efficiency, cost, and reaction time of biodiesel production. 
Based on their physical state and chemical properties, these 
catalysts are broadly categorized into homogeneous and 
heterogeneous types [66]. Homogeneous catalysts, including 
both acids and bases, are widely used due to their high activity 
and simple reaction setups, while heterogeneous and 
enzymatic catalysts offer benefits such as reusability and 
environmental compatibility. Figure 4 illustrates the main 
types of transesterification catalysts, and Table 2 compares 
their effectiveness under various reaction conditions.  

 

Figure 4. Types of catalysts for transesterification 

8. Emission characteristics 

Biodiesel produced from waste cooking oil (WCO) has 
garnered considerable interest as a sustainable substitute for 
traditional diesel fuel. The emission characteristics, 
specifically regarding COx, NOx, unburned hydrocarbons (HC), 
and particulate matter (PM), have been thoroughly examined 
[92].  

 

 



Ahad Bin Azad et al. /Future Energy                                                                                    November 2025| Volume 04 | Issue 04| Pages 09-21 

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Table 1. Comparison of physicochemical properties 

Property Unit Diesel WCO 
Density (15-20° C) Kg/m3 828.54 871 874 865 880 881 884 

Kinematic Viscosity  (40° C) cSt 2.7 4.3 3.69 4.18 6 3.58 4.95 

Pour Point ° C -37 2 -3.4 -4.5 -3 -8.4 -6 

Flash point ° C 65 133 175 202 140 170 178 

Cloud point ° C -5 6 1.6 1 -1 -1.43 0 

Iodine Value g I2/100 g - 66.52 - - 33 128.4 146.44 

Cetane Number CI 54.1 46 70.24 - 56.67 44.315 49.14 

Higher Heating Value MJ/kg 43.386 37.4 44.13 39.48 41.4 - 37.114 

Acid Value mmg KOH/g 0.2 0.92 0.39 0.3 0.8 - 0.48 

Ref.   [60] [61] [62] [63] [64] [65] [60] 
 

Table 2. Comparison of physicochemical properties 

Types of Catalyst Catalyst Methanol to Oil 
ratio 

Reaction Conditions FAME (%) Reference 

Temperature Time 

Homogeneous base 
catalyst 

KOH 6:1 65 ◦ C 1 h 93.2 
 

[67] 

NaOH 12:1 65 ◦ C 0.03 h 98.2 [68] 

CH3ONa 3.9:1 120 ◦ C 6 h 91 [69] 

CH3OK 6:1 60 ◦ C 0.5 h 99 [70] 

Homogeneous acid 
catalyst 

H2SO4 245:1 70◦ C 4 h 99 [71] 

Heterogeneous base 
catalyst 

CaO 3.5:1 130 ◦ C 1.5 h 94 [72] 

MgO 24:1 65 ◦ C 1 h 93.3 [73] 

MgO-NaOH 6:1 50 ◦ C 6 h 97 [74] 

SrO 9:1 65 ◦ C 0.07 h 93 [75] 

K3PO4 6:1 60 ◦ C 2 h 97.3 [76] 

α-Fe2O3-Al2O3 15:1 65 ◦ C 3 h 87.78 [77] 

Heterogeneous acid 
catalyst 

ZS/Si 18:1 200◦ C 10 h 98 [78] 

RS-SO3H 18:1 70 ◦ C 1 h 90.38 [79] 

ZrHPW 20:1 65 ◦ C 8 h 98.9 [80] 

SHER 12:1 60 ◦ C 2 h 97 [81] 

Fe-Al-TiO2 10:1 90 ◦ C 2.5 h 96 [82] 

Enzyme Candida 
Antarctica 
Lipase B 

4:1 40 °C 30 h 96 [83] 

Geotrichum 
candidum 

1.15:1 40 °C 1.33 h 94.1 [84] 

Immobilized 
Penicillium 

1:1 35 °C 7 h 92.8 [85] 

Pseudomonas 
cepacia 

6.6:1 38.4 °C 2.47 h 96 [86] 

Bifunctional CaO/Fe2O3 18:1 65 ◦ C 3 h 98.3 [87] 

CaO/Al2O3 12:1 60 ◦ C 3 h 98.23 [88] 

Fly ash/CaO, 
SO3 

3.1:1 59 °C 6 h 100 [89] 

Sn/CaO 16.1:1 85.15 ◦ C 3.42 h 97.39 [90] 

TiO2/PrSO3H 15:1 60 ◦ C 9 h 98.3 [91] 

 



Ahad Bin Azad et al. /Future Energy                                                                                    November 2025| Volume 04 | Issue 04| Pages 09-21 

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Its oxygen content improves combustion efficiency, 
typically reducing carbon monoxide (CO), hydrocarbons (HC), 
and particulate matter (PM) when compared to diesel. Table 
2 summarizes the emission findings documented by multiple 
researchers. 

8.1 COx emission 
CO emissions generally decrease with WCO biodiesel, 

benefiting from its higher oxygen content [93]. COx emissions 
may either stay similar or increase, depending on combustion 
efficiency and blend ratio [94]. CO2 emissions from WCO 
biodiesel can be higher or similar to those from diesel, 
depending on the combustion efficiency and blend ratio [95]. 
Enhanced oxidation typically leads to higher CO2 emissions, 
although some studies report only moderate differences [96].  

8.2 NOx Emissions 
Increased WCO biodiesel usage typically leads to higher 

NOₓ emissions, attributed to the fuel’s higher oxygen content 
and increased combustion temperatures. Advanced injection 
timing and higher bulk modulus may exacerbate NOₓ levels, 
though mitigation strategies like exhaust gas recirculation 
have proven effective.  NOₓ emissions often increase with 
higher biodiesel content, likely due to elevated in-cylinder 
temperatures and changes in ignition timing.  

8.3 Unburned HC and PM 
HC emissions typically decrease with WCO biodiesel, due 

to better combustion. PM and smoke opacity also reduce, 
especially under higher load conditions, where soot oxidation 
improves. However, some studies report minimal or 
increased PM at low loads or specific conditions [97]. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9. Performance characteristics 

The reduced calorific value, increased viscosity, and 
increased density of WCO biodiesel affect Brake Thermal 
Efficiency (BTE), Brake-Specific Fuel Consumption (BSFC), 
and Brake Power (BP), according to numerous studies. 
However, the use of additives and the optimization of engine 
parameters have shown promise in mitigating these 
drawbacks and, in some cases, enhancing performance. Table 
3 collates the findings from multiple studies. 

9.1 Brake thermal efficiency (BTE)  
Brake Thermal Efficiency (BTE) indicates the 

effectiveness with which an engine transforms the chemical 
energy of gasoline into mechanical work. Numerous studies 
demonstrate that waste cooking oil (WCO) biodiesel and its 
blends typically produce a somewhat reduced BTE relative to 
petroleum diesel, chiefly due to their diminished calorific 
value and increased viscosity. Some authors report modest 
BTE reductions of about 1–2% at higher loads or higher 
biodiesel blend ratios.  

9.2 Brake-specific fuel consumption (BSFC) 
BSFC serves as an essential metric that reflects the 

quantity of fuel utilized per unit of brake power (kW) over the 
span of one hour. A prevalent observation in the literature 
indicates that WCO biodiesel demonstrates a greater BSFC in 
comparison to diesel. The primary factors involve the reduced 
heating value, increased density, and elevated viscosity of 
WCO biodiesel, which require a marginally greater fuel mass 
injection to attain equivalent power output. Certain studies 
indicate that there are increases in BSFC within the range of 
2–17%. While others have observed more pronounced rises 
at specific loads or for higher blends.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3. Comparison of emission characteristics 

Oil Blend CO CO2 NOx HC PM Ref. 

WCMO B100 Significant 
reduction  

- Gradual Increase Significant 
Reduction 

Vast Reduction in Smoke  [98] 

WCO B100 Up to 58.9% 
Reduction 

Up to 8.6% 
reduction 

Up to 37.5% 
reduction 

- - [99] 

WCO B100 Slightly lower - Increased Slightly lower Significantly reduced [92] 

WCO B100 8.59% 
reduction 

2.62% increase 5.03% increase 30.66% 
reduction 

63.33% reduction [100] 

WCO 
(Coconut) 

B5 7.3% reduction - 1% reduction 23% reduction - [101] 

WCO B100 17.14% 
reduction 

8.05% 
reduction 

1.45% reduction - - [102] 

WCO B100 Significant 
decrease 

- Slight increase Significant 
decrease 

Sharp reduction [103] 

WCO B100 7% reduced - - Lower  - [104] 

WCO B100 - - Higher  Lower - [105] 

WCO B100 Decreased - Increased Decreased - [106] 

WCO B100 Reduced - Higher Reduced Reduced [107] 

WCMO B100 111% reduced 12% increased 9% increased 600% 
decreased 

- [108] 

WCO B100 Minimum Minimum Unreliable Minimum - [109] 

WCO B100 24.76% 
decreased 

- 15.67% increased 22.95% 
decreased 

48.13% decreased [97] 

 



Ahad Bin Azad et al. /Future Energy                                                                                    November 2025| Volume 04 | Issue 04| Pages 09-21 

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Interestingly, a few studies point to optimized blends 
(e.g., B40) or additive use (nanoparticles) mitigating the BSFC 
penalty [110]. One notable exception to this rule of thumb is 
the finding that biodiesel has a lower BSFC than diesel, put out 
by Altun et al. [111]. This raises questions about the validity 
of the results and may indicate the presence of an unusual 
experimental design or a statistical outlier. 

9.3 Brake power (BP) 
Brake Power (BP) is fundamentally influenced by the 

calorific value of the fuel as well as the quality of the air-fuel 
mixture. The reduced energy density of WCO biodiesel may 
result in diminished brake power output in comparison to 
diesel. Decreases in BP or torque are frequently associated 
with a rise in the proportion of WCO biodiesel within the 
blend. The power loss is negligible, however, for low or 
moderate blend levels and lower engine speeds, according to 
some experimental study [112]. Engine adjustments, such as 
altering injection pressure or timing, can also help to make up 
for some of the power disadvantage [113]. 

10. Combustion characteristics 

The combustion properties of waste cooking oil (WCO) 
biodiesel, such as ignition delay, peak pressure, and heat 
release, vary from those of diesel [120]. WCO blends 
demonstrate reduced ignition delays attributable to their 
elevated cetane number and oxygen content, which improve 
combustion. Due to improved combustion, WCO blends have 
a slightly greater peak pressure than diesel. However, the rate 
of pressure rise is lower since there is less fuel accumulation 
during the ignition delay. While WCO blends have a lower 
calorific value and hence a slower heat release rate, the higher 
oxygen concentration improves combustion efficiency at 
higher speeds. 

11. Conclusion 

This research emphasizes the viability of waste cooking 
oil as a sustainable and cost-effective feedstock for 
Bangladesh. The key findings of the study are as follows: 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Waste cooking oil serves as a viable and economical feedstock 
for biodiesel production in Bangladesh, with an annual 
availability surpassing one hundred thousand tons. WCO 
biodiesel typically complies with international 
physicochemical property requirements, encompassing 
acceptable limits for viscosity, density, and cetane number. 
WCO is an optimal feedstock for the production of biodiesel 
due to its ability to produce a significant quantity of FAME 
under optimal transesterification conditions, regardless of 
the type of catalyst used. The combustion of WCO biodiesel 
results in a reduction of hazardous emissions, including 
carbon monoxide (CO), hydrocarbons (HC), and particulate 
matter (PM), as compared to diesel. Despite these benefits, it 
presents certain trade-offs, including slightly reduced brake 
thermal efficiency (BTE), higher brake-specific fuel 
consumption (BSFC), and elevated NOx emissions. The 
findings indicate that WCO biodiesel is not technically viable; 
nevertheless, it is significantly pertinent to Bangladesh's 
energy and environmental requirements. Its use provides a 
dual advantage, such as functioning as a renewable energy 
source while also delivering an effective solution for 
managing waste cooking oil. Large-scale use could minimize 
production costs, reduce pollution, and prevent the harmful 
usage of WCO in the food chain. Moreover, it fulfils 
Bangladesh's commitments regarding climate change under 
the Paris agreement and decreases dependency on costly 
fossil fuel imports, hence improving national energy security. 
Future research should focus on developing practical and 
economical collection networks, enhancing pretreatment 
procedures, and advancing conversion technologies. In 
addition, continuous investigations into advanced catalysts, 
optimal blending techniques, and engine modifications are 
necessary to overcome performance limitations and ensure 
that WCO biodiesel becomes a feasible and sustainable 
contributor to Bangladesh's clean energy transition. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 4. Comparison of performance characteristics 

Reference Oil Blend 

BTE BSFC BP Load Condition 
[114] WCO  Similar to diesel Similar to diesel - Different loads, constant 

speed 
[105] WCO  

Pure 
~1–1.5% efficiency 
loss at higher loads 
vs. diesel 

Higher than diesel at a 
higher speed 

Slightly lower than 
diesel 

Various loads 

[115] WCO B100 ~6% lower than 
diesel 

~10% higher than diesel - Maximum load 

[116] WCO  
Pure 

Almost similar to 
diesel  

~17.8% higher than 
diesel  

- Full Load 

[60] WCO  
Pure 

~11.5% drop ~ 28.67% increased  ~34.5% drop 0.16–0.65 MPa 

[104] WCO 
Pure 

~1.5% higher than 
diesel 

~11.6% ↑ than diesel ~13% lower than diesel Various loads 

[117] WCO  
B40 

Slightly higher Lower than diesel  Comparable to diesel Various loads, varying 
compression 

[118] WCO B100 ~14.2% increase 
than diesel 

~3% higher than diesel 5.56% drop in power - 

[111] WCO - Lower for WCO than 
diesel 

Lower torque than diesel - 

[119] WCO B10 ~6.45% decreased ~3.3% increased ~3.8% lower than diesel Various loads 

 



Ahad Bin Azad et al. /Future Energy                                                                                    November 2025| Volume 04 | Issue 04| Pages 09-21 

16 

 

Acknowledgements 
The authors sincerely thank the research team at Green Lead 
Society for creating the platform for its contributions in 
carrying out this research project. 

Ethical issue 
The authors are aware of and comply with best practices in 
publication ethics, specifically concerning authorship 
(avoidance of guest authorship), dual submission, 
manipulation of figures, competing interests, and compliance 
with policies on research ethics. The authors adhere to 
publication requirements that the submitted work is original 
and has not been published elsewhere in any language. 

Data availability statement 
The manuscript contains all the data. However, more data will 

be available upon request from the corresponding author. 

Conflict of interest 

The authors declare no potential conflict of interest. 

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