
==== Front
MethodsX
MethodsX
MethodsX
2215-0161
Elsevier

S2215-0161(24)00399-6
10.1016/j.mex.2024.102948
102948
Energy
Biodiesel production from agricultural biomass wastes: Duroc breed fat oil, Citrillus lanatus rind, and Sorghum Bagasse
Akwenuke O.M. a
Okwelum C.O. b
Balogun T.A. c
Nwadiolu R. d
Okolotu G.I. d
Chukwuma I.E. e
Adepoju T.F. adepojut@dsust.edu.ng
f⁎
Essaghah A.E. g
Ibimilua A.F. h
Taiga A. i
a Department of Civil and Water Resources Engineering, Delta State University of Science and Technology, Ozoro, Delta State, Nigeria
b Department of Public Administrative, Faculty of Management Sciences, Delta State University of Science and Technology, P.M.B. 5, Ozoro Delta State, Nigeria
c Department of Chemical Engineering, University of Delta, Agbor, P.M.B. 2090, Agbor, Delta State, Nigeria
d Agricultural Engineering Department, Delta State University of Science and Technology, Ozoro, Delta State, Nigeria
e Department of Estate Management, Faculty of Environmental Science, Delta State University of Science and Technology, Ozoro, Delta State, Nigeria
f Chemical Engineering Department, Delta State University of Science and Technology, Ozoro, Delta State, Nigeria
g Department of Urban and Regional Planning, Faculty of Environmental Science, Delta State University of Science and Technology, Ozoro, Delta State, Nigeria
h Department of Environmental Management, Faculty of Environmental Science, Delta State University of Science and Technology, Ozoro, Delta State, Nigeria
i Department of Plant Science and Biotechnology, Faculty of Science, Delta State University of Science and Technology, Ozoro, Delta State, Nigeria
⁎ Corresponding author. adepojut@dsust.edu.ng
04 9 2024
12 2024
04 9 2024
13 10294812 6 2024
3 9 2024
© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
This research study synthesized a base catalyst from the waste Citrullus lanatus rind (WCLR) for the synthesis of biodiesel from the waste pig fat oil. The high-acid-value oil (high free fatty acid: FFA) was converted to low-acid-value oil through adsorption in sorghum bagasse ash with high particle sizes. The developed base catalyst was obtained from the WCLR and was characterized via thermogravimetric analysis (TGA), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD-FT), and Brunauer-Emmett-Teller (BET) adsorption analysis. The properties of biodiesel were compared with the recommended standard.

Results reflected that the duroc breed pig fat is rich in oil, and the oil is unsaturated. Sorghum bagasse proved to be a good bio-adsorbent for the unsaturated fat FFA reduction. The catalyst produced from WCLR was found to be rich in potassium-calcium-magnesium (K-Ca-Mg) base salts. The predicted yield of 98.69 % (wt./wt.) at 69.96 min, 79.93 °C, 3.15 % (wt.), and 8.57 (vol.) at desirability of 100 % was validated as 98.52 % (wt./wt.). Catalytic strength can be recycled in five cycles. The cost implications indicated that the cost of producing 25 L of biodiesel is $2.61.

This study proved to be the most economical way of producing biodiesel that is environmentally friendly, cost-effective, and easy to produce for future energy needs.• Oil was obtained via rendering from duroc breed waste fat oil.

• Sorghum bagasse was used as adsorbent for acid reduction of high FFA pig fat oil.

• Base catalyst used was obtained from calcined waste Citrullus lanatus rind.

Graphical abstract

Image, graphical abstract

Keywords

Citrullus lanatus rind
Duroc breed
Biodiesel
Design of Experiment
Fat oil
Rendering
Method name

Oil Rendering, Bagasse Gasification, Adsorption, Calcinations, Catalyst Characterization, Transterification, Design of Experiment
==== Body
pmcSpecifications tableSubject area:	Energy	
More specific subject area:	Biodiesel	
Name of the method:	Oil Rendering, Bagasse Gasification, Adsorption, Calcinations, Catalyst Characterization, Transterification, Design of Experiment	
Name and reference of original method:	NA	
Resource availability:	Bioreactor, Deep fryer, Sieve Sizes, thermogravimetric analysis (TGA), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD-FT), and Brunauer-Emmett-Teller (BET) analyzers, grinder, Design Expert 360, Viscometer, Burette and Pipette, Peroxide-Iodine Tester, Rotav	

Background

Convectional diesel fuel is non-environmentally friendly, highly toxic, produces emissions that release carcinogens, nitrous oxides, and soot into the atmosphere, causing greenhouse effects, and is unstable in availability [1,2]. These have caused damage to human health, such as skin cancer, eye cataracts, and immune deficiency disorders. According to the National Center for Health Statistics (NCHS), in 2023, approximately 2 million new cancer cases and approximately 600,000 cancer deaths are anticipated to occur in the US alone. Therefore, there is an urgent call to replace conventional diesel fuel with a new diesel. One way to prevent this impending danger is the use of biodiesel produced using oil, fat or algae catalyzed by waste biomass peels, such as Citrullus lanatus peel [3,4].

Pigs, also known as pork, have a belly that contains fat ranging from 65 to 75 %; the legs and the trotters have been estimated to contain about 20 % fat and 15 % fat, respectively [5]. However, of all breeds of pigs, the Duroc breed has the highest fat composition and can be found in major countries around the world. In terms of global meat intake, pigs constitute a significant portion of over 36 % (112.6 kgtons), with a projected rise to 129 kg tons by 2031. Approximately 90 % of the global output of pig fats and oils is utilized in edible items, with the majority of processing stages aimed at transforming unpalatable or unwelcome physical forms of crude fats into refined products that satisfy local food fat regulations. Steamed, boiling, or dry heat can all be used to render fat. When rendered correctly, pig fat may be almost tasteless and odorless, although its culinary attributes might vary depending on where it comes from and how it is processed. There is a range of 38–43 % for saturated fatty acids and 56–62 % for unsaturated fatty acids overall.

However, the fat, when consumed, increased the risk of developing heart problems, viral and bacterial infections, obesity, and other long-term illnesses. Furthermore, pig fat comes along with the zoonotic hepatitis E virus, which can transmit from pigs to humans [6]. Due to these, the fat has been treated as waste in many countries. This waste (fat), when converted to oil, can be used as a major raw material for biodiesel synthesis. It has been reported that the oil obtained from the fat is highly unsaturated with high FFA [6]. The unsaturated fatty acids have double bonds in the structure that causes the molecule to have bends or kinks. The bends in the molecule decrease the packing or the interaction of the fatty acid molecules with one another [6]. Acids such as HCl/H2SO4 or acidic salts have been reportedly used for the conversion of the high-FFA pig fat to a low-range acid value for easy conversion of the oil to biodiesel [6,7]. Nevertheless, there is no single report in the literature on the use of sorghum bagasse for the reduction of the acid value of pig fat oil for the synthesis of biodiesel.

Citruss lanatus peel is a waste biomass peel that has been reportedly rich in biobase mineral compounds containing majorly sodium, potassium, calcium, magnesium, and other minerals [8,9]. Since 2013, the amount of watermelon produced worldwide has increased significantly, from about 109.28 million metric tons. Considering the large amount of the fruits produced world widely, the peel can be harnessed for the synthesis of nanocatalysts for biodiesel production. This will solve the waste disposal problems and also add value to catalytic formation in the central control processing unit (CPI) in the refineries. Therefore, this research employed calcined Citrus lanatus peel as a catalyst for the production of biodiesel.

Biodiesel production processes involve the catalyzed reaction of 1 mole of triglycerides (oil) with 3 mol of alcohol. Usually, the various operating factors responsible for the optimum yield of biodiesel have been reported to be reaction time, reaction temperature, catalyst amount or concentration, and the alcohol-to-oil molar ratio, among others. The variables have been studied through an experimental design using statistical tools [10].

In the design of experiments (DOE), Matlab, Minitab, Response Surface Methodology, and Excel have been reportedly useful, but owing to advantages such as layout and design of experiments, easy variable interaction with clear curves and aids, and good visualization of responses or results with the use of surface plots, graphs make the response surface methodology stand out [2,[11], [12], [13]].

Therefore, this work harnesses the waste fat oil of pigs in the presence of an alcoholic novel catalyst obtained from Citrulus lanatus rind for biodiesel synthesis. The high-acidity oil obtained through rendering was made into low-triglycerides via sorghum bagasse as an adsorbent. The produced catalyst was characterized using FT-IR, XRF, TGA, SEM-EDS, and BET surface area measurements. The design of the experiment was carried out using response surface methodology with the aim of determining the optimum biodiesel yield. Biodiesel production was carried out in a batch reactor. The nature of biodiesel was confirmed by determining its properties and comparing them with the recommended standard [14,15]. The novel catalyst developed from rind was tested for its strength via recyclability and reusability tests.

Method details

Duroc breed pig fat rendering

Since Duroc breed pigs has the highest fat composition and can be found in major countries around the world. In terms of global meat intake, pigs constitute a significant portion of over 36 % (112.6 kgtons). Therefore, freshly harvested pig fat (2 kg) was made into smaller sizes and heated at 150 °C in an extractor until the pig fat was melted; the melted oil was allowed to cool at room temperature and then filtered into pure oil using a filtration unit. The filtered oil was kept in a 10-liter plastic keg for further processing.

Determination of FFA

The procedure for determining the FAA of the oil was as stated by Sajjad et al. [16], but with little modification. Oil of 14.1 g by weight was measured in a flat bottom flask, and 2 mL of phenolphthalein indicator was added. 12.5 mL of methanol was mixed with the oil's. The resultant solution was titrated with 0.5 M NaOH until a pink color appeared and remained steady for half an hour. Eq. (1) was used to compute the FFA of the oil. This FFA helps to determine the nature of acidity of the oil. Fats with high levels of FFA are more susceptible to oxidative aging, they become rancid more quickly.(1) FFA=14.1xVxMWX100

Where: V = Volume of NaOH, M = Molarity of NaOH, and W = Weight of the oil.

Sorghum bagasse preparation (bio-adsorbent)

Sorghum bagasse was sorted out and cleaned by manual picking; the cleaned sorghum bagasse was thermally heated in an electric oven at 180 °C for 3 h until the residual carbon was formed (carbon-based bio-adsorbent bagasse). The residual carbon base was added to 0.5 M KMnO4 to the carbon to activate for 24 h. The activated carbon was washed with distilled water, dried for 1 h at 120 °C, and then filtered through the porous mesh sizes ranging from 180, 200, 220, and 240 µm.

Activated sorghum bagasse as an adsorbent

Pig fat oil (PFO) weighing 200 g was mixed with 30 g of sorghum bagasse activated carbon (SBAC). The mixture was allowed to stand for 80 min. This mixture was properly mixed using a magnetic stirrer for 2 days, 3 days, and 4 days, respectively. The resultant mixture was filtered with filter paper, and the %FFA was gravimetrically evaluated using Eq. (1).

Catalyst preparation and characterization

Citrulus lanatus rind (CLR) was cut into small pieces and oven dried until the moisture content was <0.002. The dried CLR was milled into powder, and then sieved with mesa mesh size of 0.50 µm. The milled CLR powder was calcined in electric furnace for 4 h at 600 °C. The calcined milled CLR was allowed to stand for 48 h for proper cooling and then characterized using the procedure earlier reported by Ozioko et al. [17]. The characterization through XRD, SEM-EDX, FTIR, TGA, ZETA potential analysis, and TGA is to establish the catalytic nature, the structure and size, the sp, sp2, and sp3 functional groups associated with the single, double, and triple bonds present in the calcined CLR catalyst, as well as the isotherm adsorption studies.

Biodiesel production

The production of biodiesel was carried out using a microwave-assisted method, as earlier reported by [16], with a few modifications. In a 15-L reactor, the low-FFA oil of 300 mL was mixed with alcohol containing the calcined CLR (CCLR). The microwave power was kept between 250 and 500 W at a temperature between 60 and 80 °C, both the reactor and the bypass valves were opened, and the CCLR was passed on for 50 to 70 min. To prevent the flow back, the flow valve leading to the half is opened while the valve bypass is closed, and the mixture was separated at 8000 rpm for 10 min with a 12 V heating power. The separated layers were the glycerol (bottom) and the biodiesel (top). The glycerol was allowed through the bottom valve, while the remaining biodiesel was purified by washing with distilled water and was later dried over calcium sulfate (CaSO4). Biodiesel yield was evaluated using Eq. (2):(2) PFOBY=(WBYWFOU)X100

Where: PFOB is the pig fat oil biodiesel yield, WBYweight of biodiesel yield, WPFOU weight of pig fat oil used

Design of experiments and process optimization

Response surface methodology was used to design the experiment. Four factors with three levels were considered for design (Table 1), which generated a total of thirty experimental data points to carry out. Process optimization was carried out via numerical and graphical optimization, point prediction, confirmation, and coefficient tables (f-values, p-values, and coefficients of determination).Table 1 Design of experiment.

Table 1Name	Low	High	-alpha	+alpha	
Reaction time (min)	50	70	40	80	
Reaction temperature ( °C)	60	80	50	90	
Catalyst weight (%wt.)	2.5	3.5	2	4	
MOH/OMR (vol./vol.)	3	9	0	12	
MOH/OMR stands for methanol to oil molar ratio.

Properties of biodiesel

The properties of the produced biodiesel obtained using pig fat oil (PFO) were evaluated using the Association of Official Analytical Chemists International Official Methods of Analysis (AOAC, 1997) and Wij's method. Properties such as viscosity, moisture content, saponification, iodine, cetane number, higher heating values, and the diesel index were carried out.

Catalyst recyclability and reusability test

Catalyst recycling, refining, and reuse were carried out so as to determine the basic strength of the new novel catalyst produced from C. lanatus rind. At the end of the reaction, the catalyst recovered from the glycerol was refined by washing with alcohol and then dried in an oven for 30 min at 80 °C until a constant weight was achieved. The dried recycled catalyst was reused successively for a round of 5 cycles until there was a decrease in the yield of biodiesel noticed at the 6th and 7th cycles, hence the test was altered.

Economic analysis of the cost of production

The cost of production of the pig fat oil biodiesel was carried out so as to ascertain the viability of replacing conventional diesel with biodiesel. Since the major materials in this study were waste biomass materials, the cost of production was evaluated using Eq. (3).(3) BPC=RMC+PC+RFC+CB+CS+CCC+TC

Where: BPC is the biodiesel production cost; RMC is the raw material cost; PC is the purification cost; RFC is the rendering of fat cost; CB is the cost of burning; CS is the cost of sieving; CC is the catalyst calcined cost; and TC is the transportation cost.

Method validation

Properties of rendered pig fat oil (RPFO)

Table 2 depicts the data obtained on the properties of the rendered pig fat oil using the method of AOAC, 1997. The obtained values showed that the oil is unsaturated and contained high acid value which makes the oil unsuitable to undergo biodiesel conversion in a single stage transesterification reaction, Hence the reduction in acid value for an easy conversion was required.Table 2 Properties of RPFO.

Table 2Properties	RPFO	
Colour	Yellowish milky	
Specific gravity @ 20 °C	0.84	
Viscosity @ 40 °C/ (mm2/s)	38.65	
Moisture content (%)	<0.001	
%FFA (as oleic acid)	4.32	
Acid value (mg KOH/g oil)	8.64	
Saponification value
(mg KOH/g oil)	194.00	
Iodine value (g I2/100 g oil)	58.60	
HHV (MJ/kg)	40.11	
Cetane number	40.60	
API gravity	28.04	
Smoke point ( °C)	160 0.00	
Flash point ( °C) (D6751–07a)	204.00	
API gravity of oil >10, lighter oil, API gravity < 10, heavier oil.

Bio-adsorbent of sorghum bagasse

Since the acid value of the oil was found to be 8.64 mg KOH/g oil, this value is higher than the recommended standard for oil required for biodiesel synthesis (acid value < 3.0; FFA<1.5) [1,15]. Sorghum bagasse was used as bio-adsorbent to reduce the acid value. Fig. 1 depicts the findings of low acid values obtained using sorghum bagasse activated carbon as a bio-adsorbent after 2 days, 3 days, and 4 days, respectively. This figure showed that the low acid values were obtained at the largest particle size with the lowest FFA of 0.85 % at the 4th day (96 h).Fig. 1 Bio-adsorbent of activated sorghum bagasse in different sizes for FFA determination.

Fig 1

Novel catalyst characterization

The SEM structural image of the developed calcined catalyst (CCLR) at magnifications of 500X and 1000X is presented in Fig. 2. The black-whitish with porous pores found in the figures explained the presence of potassium, calcium, and magnesium. These elements serve as a bio-base in alcoholic catalytic conversion of low acidity oil to biodiesel. The porous pore noticed in the figures shows an excellent aid for easy alcoholic-oil interfaces reaction during transesterification process.Fig. 2 SEM strcutural images of CCLR.

Fig 2

Displayed in Fig. 3 is the FTIR analysis of the CCLR showing the functional group present in the catalyst which helps in catalytic biodiesel formation. The wide bands possesses the bending structure such as the wags and the presence of sp, sp2, and sp3 hybridization, indicating the presence of single, double, and triple bonds, respectively [18]. The peaks found around 500 to 1500 cm−1 confirmed the presence of single bonds (C-C). The peaks found in the regions of 1500 to 1900 cm−1 are classified as double bonds (C = C) groups. Those found around 1900 to 2700 cm−1 peaks region reflected the presence of triple bonds (C =C). The value of the peaks found in 2700 to 3600 cm−1 depicts the presence of single bonds to hydrogen (C – H) [[14], [15], [16], [17]].Fig. 3 FTIR analysis of CCLR.

Fig 3

The TGA analysis, which explained the decomposition of carbonate of potassium, calcium, and magnesium with the evolution of carbon (IV) oxide, is displayed in Fig. 4. The weight derivative and the weight loss against the wavelength are presented in three-dimensional plots. This indicated that the gaseous compound had been released in mass, and the temperature at which it occurred,s signified that the catalyst had completely broken down to form a pure catalyst that facilitates the production of biodiesel.Fig. 4 TGA analysis of the CCLR.

Fig 4

Observation from Fig. 5 reflected the ZETA analysis data on size distribution by intensity of the catalyst.Fig. 5 ZETA analysis of the CCLR.

Fig 5

The BET analysis evaluation of CCLR was as depicted in Table 3, which shows the Langmuir-isotherm adsorption process of the catalytic base reaction between the CCLR and the alcohol-methanol phase.Table 3 BET analysis of CCRL.

Table 3Langmuir	Isotherm	
Relative Pressure	Volume @ STP	P/Po	P/Po/W	
5.64E-02	10.2746	5.64E-02	4.39E+00	
1.18E-01	20.4013	1.18E-01	4.62E+00	
1.80E-01	30.9311	1.80E-01	4.66E+00	
2.40E-01	41.3664	2.40E-01	4.64E+00	
3.04E-01	52.7275	3.04E-01	4.61E+00	

Fig. 6 reflects the data obtained from the XRD-FS analysis of the developed bio-base catalyst used for the transesterification of oil into biodiesel. The presence of quartz, orthoclase, mica-phylosilicates, and albite salts indicated the presence of potassium-calcium-magnesium-aluminate found in the CCLR.Fig. 6 XRD-FS analysis of CCLR.

Fig 6

Production of biodiesel

Experimental data and process optimization

Displayed in Table 4 are the variables factors, the experimental outcomes, and the predicted values by the response surface methodology design using central composite design. The table depicts the highest DPFOB yield of 98.41 % (wt./wt.) at run 7 and a low yield of 88.18 % (wt./wt.) at run 17.Table 4 Experimental outcome and the predicted responses.

Table 4Runs	K1 (min)	K2 ( °C)	K3 %(wt.)	K4 (vol./vol.)	DPFOB %(wt./wt.)	PDPFOB %(wt./wt.)	
1	0.000	0.000	0.000	0.000	88.89	88.80	
2	0.000	0.000	0.000	0.000	94.60	94.55	
3	0.000	0.000	0.000	0.000	90.44	90.77	
4	0.000	0.000	0.000	0.000	93.96	93.85	
5	0.000	0.000	0.000	0.000	96.32	96.21	
6	0.000	0.000	0.000	0.000	94.50	94.55	
7	0.000	0.000	0.000	2.000	98.24	98.41	
8	0.000	0.000	0.000	−1.000	94.93	94.88	
9	0.000	0.000	2.000	0.000	85.81	85.69	
10	0.000	0.000	−2.000	0.000	87.93	87.87	
11	0.000	2.000	0.000	0.000	91.48	91.65	
12	0.000	−2.000	0.000	0.000	94.60	94.55	
13	2.000	0.000	0.000	0.000	90.97	91.12	
14	−2.000	0.000	0.000	0.000	92.76	92.93	
15	1.000	1.000	1.000	1.000	96.31	96.26	
16	−1.000	1.000	1.000	1.000	88.34	88.22	
17	1.000	−1.000	1.000	1.000	88.25	88.18	
18	−1.000	−1.000	1.000	1.000	94.60	94.55	
19	1.000	1.000	−1.000	1.000	91.39	91.28	
20	−1.000	1.000	−1.000	1.000	95.38	95.55	
21	1.000	−1.000	−1.000	1.000	88.58	88.46	
22	−1.000	−1.000	−1.000	1.000	98.46	97.90	
23	1.000	1.000	1.000	−1.000	92.85	92.80	
24	−1.000	1.000	1.000	−1.000	91.61	91.78	
25	1.000	−1.000	1.000	−1.000	94.40	94.55	
26	−1.000	−1.000	1.000	−1.000	93.36	93.31	
27	1.000	1.000	−1.000	−1.000	90.18	90.34	
28	−1.000	1.000	−1.000	−1.000	94.50	94.55	
29	1.000	−1.000	−1.000	−1.000	86.81	86.75	
30	−1.000	−1.000	−1.000	−1.000	94.70	94.87	
K1 = reaction time, K2 = reaction temperature; K3 = catalyst amount, K4 = MOH/OMR.

Presented in Table 5 is the analysis based on ANOVA (analysis of variance) for the 2nd-order polynomial with fits statistics. All factors as well as the combinations were highly significant at p-value<0.05, except the K1K3 (p-value = 0.0933) and the K12 (p-value = 0.5214) that were found insignificant.Table 5 2nd order of polynomial and fits statistic.

Table 5Source	SS	df	MS	f-value p-value	
Model	320.55	14	22.90	437.34	< 0.0001	
K1	6.45	1	6.45	123.16	< 0.0001	
K2	7.53	1	7.53	143.76	< 0.0001	
K3	14.35	1	14.35	274.15	< 0.0001	
K4	199.63	1	199.63	3812.99	< 0.0001	
K1K2	21.25	1	21.25	405.93	< 0.0001	
K1K3	0.1681	1	0.1681	3.21	0.0933	
K1K4	8.15	1	8.15	155.69	< 0.0001	
K2K3	16.44	1	16.44	314.07	< 0.0001	
K2K4	2.59	1	2.59	49.51	< 0.0001	
K12	5.71	1	5.71	109.11	< 0.0001	
K22	0.8766	1	0.8766	16.74	0.0010	
K32	0.0226	1	0.0226	0.4312	0.5214	
K42	2.57	1	2.57	49.11	< 0.0001	
Fits statistics						
R²	0.9976	Std. Dev.	0.2288	–	–	
Adjusted R²	0.9953	Mean	92.50	–	-	
Predicted R²	0.9853	C.V. %	0.2473	–	–	
Adeq Precision	78.6075	–	-	-	–	
SS = sum of the squares, df = degree of freedom, MS = means squares, f-value = fit values, p-value = probability values.

The predicted yield of 98.69 %(wt./wt.) at 69.96 min, 79.93 °C, 3.15 %(wt.), and 8.57 (vol.vol.) at desirability of 100 % was validated as 98.52 %(wt./wt.) [[18], [19], [20]]. The established model coded equation that predicts the response DPFOB yield was as presented in Eq. (4).(4) DPFOB%(wt./wt.)=347.52+24.30K1+85.01K2+8.53K3+3.26K4+1.15K1K2+−0.1025K1K3+0.7138K1K4−1.01K2K3+0.4025K2K4−0.1772K12−0.0284K22−0.3034K32−2.49K42

The complex relationship, patterns, and trends in data between the response (DPFOB), desirability, and the four factors (K1, K2, K3, and K4) are presented in Fig. 7.Fig. 7 Complex relationship, patterns, and the trends.

Fig 7

Nature of biodiesel as compared with international standards

Displayed in Table 6 are the properties of the produced biodiesel with respect to international standards [14,15]. The value obtained confirmed the produced biodiesel from pig fat oil fit well with the recommended standard and that the fuel is environmentally friendly.Table 6 Properties of the DPFOB.

Table 6Parameter	DPFOB	[14]	[15]	
Colour	Yellowish brown	–	–	
Specific gravity @ 20 °C	0.88	–	0.86–0.90	
Viscosity @ 40 °C/ (mm2/s)	3.20	1.9–6.0	3.5–5.0	
Moisture content (%)	<0.001	<0.03	0.02	
%FFA (as oleic acid)	0.20	0.40 max	0.25 max	
Acid value (mg KOH/g oil)	0.40	0.80 max	0.5 max	
Saponification value
(mg KOH/g oil)	176	–	120 max	
Iodine value (g I2/100 g oil)	52.80	–	–	
HHV (MJ/kg)	41.43	–	12.85 min	
Cetane number	65.43	–	–	
API gravity	45.38	57 min	51 min	
Smoke point ( °C)	152 0.00	–	–	
Diesel index	76.99	–	–	
Pour point	+7	–	−15 to 10	
Cloud point	+10	–	−3 to 12	
Flash point	138	–	130 min	

Catalytic strength test

Depicted in Fig. 8 are the plots of the catalyst (CCLR) strength tests via reusability in various cycles. It was observed that the yield of biodiesel decreased at the 6th and 7th cycles; hence, the test was altered [[21], [22], [23], [24]], indicating the advantages of using a novel heterogeneous catalyst over the homogeneous conventional base.Fig. 8 Catalytic strength test CCLR.

Fig 8

Assessments of cost estimation of DPFOB

Table 7 shows the cost estimate of producing 25 L of biodiesel from 100 kg of fat obtained from duroc pig fat. The cost implications, when compared with the cost of conventional diesel, indicated that the biodiesel produced in this study is not only environmentally friendly but also cost-effective and can be used as a replacement for diesel in the future in the future for green energy.Table 7 Estimate of DPFOB produced.

Table 7Abbreviations	Items	Cost	Total cost	
RMC	Raw Material Cost (Freely obtained) Fat and Citrullus lanatus Rind	0.00	0.00	
PC	Purification Cost (Ionised water from laboratory was used) (washing of fat and biodiesel)	0.00	0.00	
RFC	Rendering of Fat Cost for 2 h (500/h)	500 × 2	1000	
CB	Cost of Burning (sorghum bagasse) (150/h)	100 × 3	300	
CS	Cost of Sieving (Laboratory magnetic sieved was used)	0.00	0.00	
CC	Catalyst Calcined Cost (150/h)	150 × 4	600	
TC	Transportation Cost	2000	2000	
TOTAL	3900	

The above estimate indicates that the cost of producing 1 L of biodiesel is (3900/25) = 150.00/L. The cost of 1 L of diesel as of June 7, 2024 is 1100/L. Estimating this in dollars ($), the cost of producing 25 L of biodiesel is $2.61 of DPFOB [[25], [26], [27]].

This study proved to be the most economical way of producing biodiesel that is environmentally friendly, cost-effective, and easy to produce for future energy needs.

Limitations

This work is limited to the use of animal waste fats, specifically the pig fat of the Duroc breed. The work is also a laboratory-scale production.

Ethics statements

The work does not involve the use of animal or human objects.

CRediT authorship contribution statement

O.M. Akwenuke: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation. C.O. Okwelum: Writing – original draft, Formal analysis, Investigation, Supervision, Methodology. T.A. Balogun: Supervision, Methodology, Software, Validation, Formal analysis, Methodology. R. Nwadiolu: Supervision, Methodology, Software, Validation, Formal analysis, Methodology. G.I. Okolotu: Writing – original draft, Investigation, Resources, Formal analysis, Investigation. I.E. Chukwuma: Writing – original draft, Investigation, Resources, Formal analysis, Investigation. T.F. Adepoju: Formal analysis, Resources, Data curation, Writing – original draft. A.E. Essaghah: Data curation, Methodology. A.F. Ibimilua: Formal analysis, Resources, Data curation, Writing – original draft. A. Taiga: Supervision, Methodology, Software.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

No data was used for the research described in the article.

Acknowledgments

Special thanks to technical staff of Spectral Laboratory Services of Engineering and Science Analyses, Tudunwada Kaduna South, Kaduna, Nigeria.

Related research article: None.
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