Unlocking the Power of Waste Cooking Oils for Sustainable Energy Production and Circular Economy: A Review

Main Article Content

Samson Onoriode Okpo
Emozino Donatus Edafiadhe


In the pursuit for sustainable energy solutions, biodiesel has come to prominence as an alternative to petroleum-derived diesel. This review delves into cutting-edge developments in production of biodiesel, emphasizing use of waste cooking oils (WCOs) as an environmentally friendly raw material. Incorporating waste cooking oils (WCOs) into the biodiesel production process not only tackles environmental issues associated with improper disposal but also adheres to the principles of a circular economy. This manuscript covers various methods and technologies for converting WCOs into high-quality biodiesel, emphasizing economic viability and environmental benefits. It discusses the potential of WCO-derived biodiesel to meet stringent fuel standards and reduce greenhouse gas emissions. Significant progress has been made in using waste cooking oils to generate sustainable energy, aligning with broader initiatives focused on renewable energy and circular economy principles. In summary, the utilization of waste cooking oils for biodiesel production presents an opportunity to shift away from reliance on fossil fuels, thereby fostering circular economy practices and sustainability goals.

Article Details

How to Cite
S. O. Okpo and E. D. Edafiadhe, “Unlocking the Power of Waste Cooking Oils for Sustainable Energy Production and Circular Economy: A Review”, AJERD, vol. 7, no. 1, pp. 41-55, Mar. 2024.


[1] Nalley, S., & LaRose, A. (2021). International energy outlook 2021, US Department of Energy: Washington, DC, USA. 1-21.
[2] ASTM D6751-08- Standard specification for biodiesel fuel (B100) blend stock for distillate fuels, In: Annual Book of ASTM Standards, ASTM International, West Conshohocken, Method D6751-08, 2008a.
[3] Ziolkowska, J. R. (2020). Biofuels technologies: An overview of feedstocks, processes, and technologies, Biofuels for a More Sustainable Future, 1–19.
[4] Malode, S. J., Gaddi, S. A. M., Kamble, P. J., Nalwad, A. A., Muddapur, U. M., & Shetti, N. P. (2022). Recent evolutionary trends in the production of biofuels, Materials Science for Energy Technologies, 5, 262-277.
[5] Maliha, A., Abu-Hijleh, B. A review on the current status and post-pandemic prospects of third-generation biofuels, Energy Systems, 14(4), 1185–1216.
[6] Powar, R. S., Yadav, A. S., Ramakrishna, C. S., Patel, S., Mohan, M., Sakharwade, S. G., Choubey, M., Ansu, A.K, & Sharma, A. (2022). Algae: A potential feedstock for third generation biofuel, Materials Today: Proceedings, 63, A27-A33.
[7] Veluru, S., Hamzah, H.T., Tukaram Bai, M, Poiba, V.R. & Mahdi, H.S. (2022). A Review on biodiesel production from various feedstocks by transesterification, IOP Conf. Series: Materials Science and Engineering, 1258(1), 012024.
[8] Singh, D., Sharma, D., Soni, S. L., Sharma, S., Kumar Sharma, P. & Jhalani, A. (2019). A review on feedstocks, production processes, and yield for different generations of biodiesel, Fuel, 262, 116553.
[9] Paschalidou, A., Tsatiris, M. & Kitikidou, K. (2016). Energy crops for biofuel production or for food? - SWOT analysis (case study: Greece), Renewable Energy, 93, 636-647.
[10] Adenuga, A. A., Oyekunle, J. A. O. & Idowu, O. O. (2021). Pathway to reduce free fatty acid formation in Calophyllum inophyllum kernel oil: A renewable feedstock for biodiesel production, Journal of Cleaner Production, 316, 128222.
[11] Athar, M. & Zaidi, S. (2020). A review of the feedstocks, catalysts, and intensification techniques for sustainable biodiesel production, Journal of Environmental Chemical Engineering, 8(6), 104523.
[12] Awogbemi, O., Von Kallon, D. V., Aigbodion, V. S. & Panda, S. (2021b). Advances in biotechnological applications of waste cooking oil, Case Studies in Chemical and Environmental Engineering, 4, 100158.
[13] Khan, H. M., Iqbal, T., Yasin, S., Irfan, M., Kazmi, M., Fayaz, H. & Ullah, N. (2021). Production and utilization aspects of waste cooking oil based biodiesel in Pakistan, Alexandria Engineering Journal, 60(6), 5831–5849.
[14] Teixeira, M. R., Nogueira, R. & Nunes, L. M. (2018). Quantitative assessment of the valorisation of used cooking oils in 23 countries, Waste management, 78, 611-620.
[15] Yusuff, A. S., Adeniyi, O. D., Olutoye, M. A. & Akpan, U. G. (2018). Waste frying oil as a feedstock for biodiesel production, in Petroleum Chemicals-Recent Insight, ed. M. Zoveidavianpoor, IntechOpen, London, UK, 5-24.
[16] Topi, D. (2020). Transforming waste vegetable oils to biodiesel, establishing of a waste oil management system in Albania, SN Applied Sciences, 2, 1-7.
[17] Sarno, M., & Iuliano, M. (2019). Biodiesel production from waste cooking oil, Green Processing and Synthesis, 8(1), 828-836.
[18] Casallas, I. D., Carvajal, E., Mahecha, E., Castrillon, C., Gomez, H., Lopez, C. & Malagon-Romero, D. (2018). Pre-treatment of waste cooking oils for biodiesel production, Chemical Engineering Transactions, 65, 385-390.
[19] Saini, R. D. (2017). Conversion of waste cooking oil to biodiesel, International Journal of Petroleum Science and Technology, 11(1), 9-21.
[20] Math, M. C., Kumar, S. P., & Chetty, S. V. (2010). Technologies for biodiesel production from used cooking oil - A review, Energy for Sustainable Development, 14(4), 339-345.
[21] Maddikeri, G. L., Pandit, A. B., & Gogate, P. R. (2012). Intensification approaches for biodiesel synthesis from waste cooking oil: a review, Industrial & Engineering Chemistry Research, 51(45), 14610-14628.
[22] Statista (2023). Global production of vegetable oils from 2000/01 to 2022/23 (in million metric tons), Statista Research Department. https://www.statista.com/statistics/263978/global-vegetable-oil-production-since-2000-2001/. Assessed Online 24/08/2023 at 9.30am
[23] EUBIA - The European Biomass Industry Association (2015). Transformation of used cooking oil into biodiesel: from waste to resource, Technical Report of European Biomass Industry Association. 1-8.
[24] Mannu, A., Ferro, M., Pietro, M. E. D., & Mele, A. (2019). Innovative applications of waste cooking oil as raw material, Science Progress, 102(2), 153-160.
[25] Adepoju, T. F., & Olawale, O. (2014). Acid-catalyzed esterification of waste cooking oil with high FFA for biodiesel production, Chemical and process engineering research, 21, 80-85.
[26] Foo, W. H., Chia, W. Y., Tang, D. Y. Y., Koay, S. S. N., Lim, S. S., & Chew, K. W. (2021). The conundrum of waste cooking oil: Transforming hazard into energy, Journal of hazardous materials, 417(2021), 126129.
[27] Aderibigbe, F. A., Saka, H. B., Mustapha, S. I., Amosa, M. K., Shiru, S., Tijani, I. A., Babatunde, E.O., & Bello, B. T. (2023). Waste Cooking Oil Conversion to Biodiesel Using Solid Bifunctional Catalysts, ChemBioEng Reviews, 10(3), 293-310.
[28] Salihu, A., Mahmood, A. A., Gimba, S. B., Nzerem, P., & Okafor, I. (2021). Production of biodiesel from waste cooking oil by transesterification process using heterogeneous catalyst, Nigerian Journal of Environmental Sciences and Technology (NIJEST) 5(2), 501-510.
[29] Falowo, O. A., Oladipo, B., Taiwo, A. E., Olaiya, A. T., Oyekola, O. O., & Betiku, E. (2022). Green heterogeneous base catalyst from ripe and unripe plantain peels mixture for the transesterification of waste cooking oil, Chemical Engineering Journal Advances, 10, 100293.
[30] Amenaghawon, A. N., Obahiagbon, K., Isesele, V., & Usman, F. (2022). Optimized biodiesel production from waste cooking oil using a functionalized bio-based heterogeneous catalyst, Cleaner Engineering and Technology, 8, 100501.
[31] Linganiso, E. C., Tlhaole, B., Magagula, L. P., Dziike, S., Linganiso, L. Z., Motaung, T. E., Moloto, N., & Tetana, Z. N. (2022). Biodiesel production from waste oils: a South African outlook, Sustainability, 14(4), 1983.
[32] Osagiede, C. A., & Aisien, F. A. (2024). Biochar-based bi-functional catalyst derived from rubber seed shell and eggshell for biodiesel production from waste cooking oil, Fuel, 358, 130076.
[33] Fernandez, C., Bernal, A., Leon, P., Gelves, O., & Malagon-Romero, D. H. (2022). Optimization of a Route for Collecting Waste Cooking Oil in Bogotá, Chemical Engineering Transactions, 91, 625-630.
[34] Tsai, W. T. (2019). Mandatory recycling of waste cooking oil from residential and commercial sectors in Taiwan, Resources, 8(1), 38.
[35] Van Grinsven, A., Van den Toorn, E., Van der Veen, R., & Kampman, B (2020). Used Cooking Oil (UCO) as a biofuel feedstock in the EU, Publications of CE Delft, 1-65.
[36] De Feo, G., Di Domenico, A., Ferrara, C., Abate, S., & Sesti Osseo, L. (2020). Evolution of waste cooking oil collection in an area with long-standing waste management problems, Sustainability, 12(20), 8578
[37] Febijanto, I., Ulfah, F. & Trihadi, S. E. Y. (2023). A Review on used cooking oil as a sustainable biodiesel feedstock in Indonesia, In IOP Conference Series: Earth and Environmental Science, 1187(1), 012011.
[38] Cárdenas, J., Orjuela, A., Sánchez, D. L., Narváez, P. C., Katryniok, B. & Clark, J. (2021). Pre-treatment of used cooking oils for the production of green chemicals: A review, Journal of Cleaner Production, 289, 125129.
[39] Matusinec, J., Hrabec, D., Šomplák, R., Nevrlý, V., & Redutskiy, Y. (2022). Cooking oils and fat waste collection infrastructure planning: a regional-level outline, Clean Technologies and Environmental Policy, 24(1), 109-123.
[40] Loizides, M. I., Loizidou, X. I., Orthodoxou, D. L., & Petsa, D. (2019). Circular bioeconomy in action: collection and recycling of domestic used cooking oil through a social, reverse logistics system, Recycling, 4(2), 16.
[41] Susilowati, E., Hasan, A., & Syarif, A. (2019). Free fatty acid reduction in a waste cooking oil as a raw material for biodiesel with activated coal ash adsorbent, Journal of Physics: Conference Series, 1167(1), 012035.
[42] Biofuels International. (2021).The conversion of used cooking oils into biodiesel, https:// biofuels-news.com/news/the-conversion-of-used-cooking-oils-into-biodiesel/
[43] Danane, F., Bessah, R., Alloune, R., Tebouche, L., Madjene, F., Kheirani, A.Y., & Bouabibsa, R. (2022). Experimental optimization of Waste Cooking Oil ethanolysis for biodiesel production using Response Surface Methodology (RSM), Science and Technology for Energy Transition, 77(14), 1-10.
[44] Kedir, W. M., Wondimu, K. T., & Weldegrum, G. S. (2023). Optimization and characterization of biodiesel from waste cooking oil using modified CaO catalyst derived from snail shell, Heliyon, 9(5), 1-13.
[45] Tsoutsos, T. D., Tournaki, S., Paraíba, O., & Kaminaris, S. D. (2016). The Used Cooking Oil-to-biodiesel chain in Europe assessment of best practices and environmental performance, Renewable and sustainable energy reviews, 54, 74-83.
[46] Kristiana, T., O’Connell, A., & Baldino, C. (2023). Producing high quality biodiesel from used cooking oil in Indonesia, ICCT working paper, 2023-18, 1-15.
[47] Gurdil, G. A. K., Kabutey, A., Selvi, K. Ç., Hrabe, P., Herak, D., & Frankova, A. (2020). Investigation of heating and freezing pretreatments on mechanical, chemical and spectral properties of bulk sunflower seeds and oil, Processes, 8(4), 411.
[48] Neuman, T. (2014). Use of separators, decanters in biodiesel processing, Biodiesel Magazine. https://biodieselmagazine.com/articles/use-of-separators-decanters-in-biodiesel-processing-17995 [online: assessed 26th December 2023, 1.20pm]
[49] Ju, J., Zheng, Z., Xu, Y., Cao, P., Li, J., Li, Q. & Liu, Y. (2019). Influence of total polar compounds on lipid metabolism, oxidative stress and cytotoxicity in HepG2 cells, Lipids in Health and Disease, 18(1), 1-13.
[50] Foo, W. H., Koay, S. S. N., Tang, D. Y. Y., Chia, W. Y., Chew, K. W., & Show, P. L. (2022). Safety control of waste cooking oil: transforming hazard into multifarious products with available pre-treatment processes, Food Materials Research, 2(1), 1-11.
[51] Mamtani, K., Shahbaz, K., & Farid, M. M. (2021). Glycerolysis of free fatty acids: a review, Renewable and Sustainable Energy Reviews, 137, 110501.
[52] Ennetta, R., Soyhan, H. S., Koyunoglu, C., & Demir, V. G. (2022). Current technologies and future trends for biodiesel production: a review, Arabian Journal for Science and Engineering, 47(12), 15133-15151.
[53] Salaheldeen, M., Mariod, A. A., Aroua, M. K., Rahman, S. A., Soudagar, M. E. M. & Fattah, I. R. (2021). Current state and perspectives on transesterification of triglycerides for biodiesel production, Catalysts, 11(9), 1121.
[54] Singh, D., Sharma, D., Soni, S. L., Inda, C. S., Sharma, S., Sharma, P. K, & Jhalani, A. (2021). A comprehensive review of biodiesel production from waste cooking oil and its use as fuel in compression ignition engines: 3rd generation cleaner feedstock, Journal of Cleaner Production, 307, 127299.
[55] Saad, M., Siyo, B., & Alrakkad, H. (2023). Preparation and characterization of biodiesel from waste cooking oils using heterogeneous Catalyst (Cat. TS-7) based on natural zeolite, Heliyon, 9(6), 1-13.
[56] Degfie, T. A., Mamo, T. T., & Mekonnen, Y. S. (2019). Optimized Biodiesel Production from Waste Cooking Oil (WCO) using Calcium Oxide (CaO) Nano-catalyst, Scientific Reports, 9(1), 18982.
[57] Sakthivel, R., Ramesh, K., Purnachandran, R., & Shameer, P. M. (2018). A review on the properties, performance and emission aspects of the third generation biodiesels, Renewable and Sustainable Energy Reviews, 82, 2970-2992.
[58] EN 14214- Committee for Standardization Automotive fuels—fatty acid methyl esters (FAME) for diesel engines—requirements and test methods, European Committee for Standardization, Brussels; 2003a. Method EN 14214.
[59] Wang, B., Wang, B., Shukla, S. K., & Wang, R. (2023). Enabling catalysts for biodiesel production via transesterification, Catalysts, 13(4), 740.
[60] Mandari, V., & Devarai, S.K. (2022). Biodiesel Production Using Homogeneous, Heterogeneous, and Enzyme Catalysts via Transesterification and Esterification Reactions: a Critical Review, Bioenergy Research, 15, 935–961.
[61] Vilas Boas, R.N., & Mendes, M.F. (2022). A review of biodiesel production from non-edible raw materials using the transesterification process with a focus on influence of feedstock composition and free fatty acids, Journal of the Chilean Chemical Society, 67(1), 5433-5444.
[62] Pikula, K., Zakharenko, A., Stratidakis, A., Razgonova, M., Nosyrev, A., Mezhuev, Y., Tsatsakis, A. & Golokhvast, K. (2020). The advances and limitations in biodiesel production: feedstocks, oil extraction methods, production, and environmental life cycle assessment, Green Chemistry Letters and Reviews, 13(4), 275-294.
[63] Singh, C. S., Kumar, N., & Gautam, R. (2021). Supercritical transesterification route for biodiesel production: Effect of parameters on yield and future perspectives, Environmental Progress & Sustainable Energy, 40(6), e13685.
[64] Neupane, D. (2022). Biofuels from Renewable Sources, a potential option for biodiesel production, Bioengineering, 10(1), 1-29.
[65] Gaurav, A., Ng, F. T., & Rempel, G. L. (2016). A new green process for biodiesel production from waste oils via catalytic distillation using a solid acid catalyst–Modeling, economic and environmental analysis, Green Energy & Environment, 1(1), 62-74.
[66] Goortani, B. M., Gaurav, A., Deshpande, A., Ng, F. T., & Rempel, G. L. (2015). Production of isooctane from isobutene: energy integration and carbon dioxide abatement via catalytic distillation. Industrial & Engineering Chemistry Research, 54(14), 3570-3581.
[67] Pascoal, C. V. P., Oliveira, A. L. L., Figueiredo, D. D., & Assunção, J. C. C. (2020). Optimization and kinetic study of ultrasonic-mediated in situ transesterification for biodiesel production from the almonds of Syagrus cearensis. Renewable Energy, 147, 1815-1824.
[68] Moazeni, F., Chen, Y. C., & Zhang, G. (2019). Enzymatic transesterification for biodiesel production from used cooking oil, a review, Journal of cleaner production, 216, 117-128.
[69] Bagal, M.V., Shaju, M., Yadav, A., & Chavan, S. (2020). Review: enzymatic tranesterification of waste, Journal of Emerging Technologies and Innovative Research (JETIR), 7(6), 1132-1142.
[70] Patil, P. D., Reddy, H., Muppaneni, T., & Deng, S. (2017). Biodiesel fuel production from algal lipids using supercritical methyl acetate (glycerin-free) technology, Fuel, 195, 201-207.
[71] Pal, A., Verma, A., Kachhwaha, S. S., & Maji, S. (2010). Biodiesel production through hydrodynamic cavitation and performance testing, Renewable Energy, 35(3), 619-624.
[72] Andreani, L., & Rocha, J. D. (2012). Use of ionic liquids in biodiesel production: a review, Brazilian Journal of Chemical Engineering, 29(1), 1-13.
[73] Cheng, J., Mao, Y., Guo, H., Qian, L., Shao, Y., Yang, W., & Park, J. Y. (2022). Synergistic and efficient catalysis over Brønsted acidic ionic liquid [BSO3HMIm][HSO4]–modified metal–organic framework (IRMOF-3) for microalgal biodiesel production, Fuel, 322, 124217.
[74] Zhang, Q., Hu, Y., Li, S., Zhang, M., Wang, Y., Wang, Z., & Pan, H. (2022). Recent advances in supported acid/base ionic liquids as catalysts for biodiesel production, Frontiers in Chemistry, 10, 999607.
[75] Gholami, A., Pourfayaz, F., & Maleki, A. (2020). Recent advances of biodiesel production using ionic liquids supported on nanoporous materials as catalysts: a review, Frontiers in Energy Research, 8, 144.
[76] Troter, D. Z., Todorović, Z. B., Đokić-Stojanović, D. R., Stamenković, O. S., & Veljković, V. B. (2016). Application of ionic liquids and deep eutectic solvents in biodiesel production: A review, Renewable and Sustainable Energy Reviews, 61, 473-500.
[77] Liu, C. Z., Wang, F., Stiles, A. R., & Guo, C. (2012). Ionic liquids for biofuel production: opportunities and challenges, Applied energy, 92, 406-414.
[78] Ramadhan, A.R., Pornwongthong, P., Rattanaporn, K., & Sriariyanun, M. (2015). Review of Ionic Liquid as a Catalyst for Biodiesel Production, Journal of Science and Technology MSU, 34(4), 404-412.
[79] Chintagunta, A.D., Zuccaro, G., Kumar, M., Kumar, S. J., Garlapati, V.K., Postemsky, P.D., Sampath Kumar, N.S., Chandel, A.K., & Simal-Gandara, J. (2021). Biodiesel production from lignocellulosic biomass using oleaginous microbes: prospects for integrated biofuel production, Frontiers in Microbiology, 12, 1-23.
[80] Shi, S., Valle‐Rodríguez, J. O., Siewers, V., & Nielsen, J. (2011). Prospects for microbial biodiesel production, Biotechnology journal, 6(3), 277-285.
[81] Sharma, A., Kodgire, P., & Kachhwaha, S. S. (2019). Biodiesel production from waste cotton-seed cooking oil using microwave-assisted transesterification: Optimization and kinetic modeling, Renewable and Sustainable Energy Reviews, 116, 109394.
[82] Nayak, S. N., Bhasin, C. P., & Nayak, M. G. (2019). A review on microwave-assisted transesterification processes using various catalytic and non-catalytic systems, Renewable Energy, 143, 1366-1387.
[83] El Sherbiny, S. A., Refaat, A. A., & El Sheltawy, S. T. (2010). Production of biodiesel using the microwave technique, Journal of Advanced Research, 1(4), 309-314.
[84] Palma, V., Barba, D., Cortese, M., Martino, M., Renda, S. & Meloni, E. (2020). Microwaves and heterogeneous catalysis: A review on selected catalytic processes, Catalysts, 10(2), 246.
[85] Martinez-Guerra, E., & Gude, V. G. (2015). Continuous and pulse sonication effects on transesterification of used vegetable oil, Energy Conversion and Management, 96, 268-276.
[86] Riyanto, T., Istadi, I., Buchori, L., Anggoro, D. D., & Dani Nandiyanto, A. B. (2020). Plasma-assisted catalytic cracking as an advanced process for vegetable oils conversion to biofuels: A mini review, Industrial & Engineering Chemistry Research, 59(40), 17632-17652.
[87] Cubas, A. L. V., Machado, M. M., Pinto, C. R. S. C., Moecke, E. H. S., & Dutra, A. R. A. (2016). Biodiesel production using fatty acids from food industry waste using corona discharge plasma technology, Waste management, 47, 149-154.
[88] Karki, S., Sanjel, N., Poudel, J., Choi, J. H., & Oh, S. C. (2017). Supercritical transesterification of waste vegetable oil: characteristic comparison of ethanol and methanol as solvents, Applied Sciences, 7(6), 632.
[89] Kulkarni, M. G., & Dalai, A. K. (2006). Waste cooking oil an economical source for biodiesel: a review, Industrial & engineering chemistry research, 45(9), 2901-2913.
[90] Okoro, O. V., Sun, Z., & Birch, J. (2018). Catalyst-free biodiesel production methods: A comparative technical and environmental evaluation, Sustainability, 10(1), 1-22.
[91] Oliveira, P. A., Baesso, R. M., Moraes, G. C., Alvarenga, A. V., & Costa-Félix, R. P. (2018). Ultrasound methods for biodiesel production and analysis, Biofuels-State of Development, 121-148.
[92] Oliveira, P. A., Baesso, R. M., Morais, G. C., Alvarenga, A. V., & Costa-Félix, R. P. (2021). Ultrasound-assisted transesterification of soybean oil using low power and high frequency and no external heating source, Ultrasonics Sonochemistry, 78(2021), 1-9.
[93] Geissdoerfer, M., Savaget, P., Bocken, N. M., & Hultink, E. J. (2017). The Circular Economy–A new sustainability paradigm? Journal of cleaner production, 143, 757-768.
[95] Cho, S., Kim, J., Park, H. C., & Heo, E. (2015). Incentives for waste cooking oil collection in South Korea: a contingent valuation approach, Resources, Conservation and Recycling, 99, 63-71.
[96] Alias, N. I., Jayakumar, J. K., & Zain, S. M. (2018). Characterization of waste cooking oil for biodiesel production, Jurnal Kejuruteraan, 1(2), 79-83.
[97] Ganesan, K., Sukalingam, K., & Xu, B. (2019). Impact of consumption of repeatedly heated cooking oils on the incidence of various cancers- A critical review, Critical Reviews in Food Science and Nutrition, 59(3), 488-505.
[98] Lopes, M., Miranda, S. M., & Belo, I. (2020). Microbial valorization of waste cooking oils for valuable compounds production–a review, Critical Reviews in Environmental Science and Technology, 50(24), 2583-2616.
[99] United Nations General Assembly. (2015). Transforming our world: the 2030 agenda for sustainable development (A/RES/70/1). Retrieved from https://sustainabledevelopment.un.org/post2015/transformingourworld
[100] Gebremariam, S. N., & Marchetti, J. M. (2018). Economics of biodiesel production, Energy Conversion and 660 Management, 168, 74-84.
[101] Karmee, S. K., Patria, R. D., & Lin, C. S. K. (2015). Techno-economic evaluation of biodiesel production from waste cooking oil—a case study of Hong Kong, International journal of molecular sciences, 16(3), 4362-4371.
[102] Keera, S. T., El Sabagh, S. M., & Taman, A. R. (2011). Transesterification of vegetable oil to biodiesel fuel using alkaline catalyst, Fuel, 90(1), 42-47.
[103] Avinash, A., & Murugesan, A. (2017). Economic analysis of biodiesel production from waste cooking oil, Energy Sources, Part B: Economics, Planning, and Policy, 12(10), 890-894.
[104] Mohammadshirazi, A., Akram, A., Rafiee, S., & Kalhor, E. B. (2014). Energy and cost analyses of biodiesel production from waste cooking oil. Renewable and sustainable energy reviews, 33(1), 44-49.