Sustainable Biofuel Production from Agricultural By-Products: Citrus Peels and Pumpkin Seeds as Feedstocks for Bioethanol and Biodiesel

Year 2025, Volume: 35 Issue: 3, 533 - 544, 30.09.2025

Riham Bakr , Maryam Sameh Fathi , Maria Adel , Bola Fouad , Rahma Sayed

https://doi.org/10.29133/yyutbd.1559061

Abstract

Energy is fundamental to development, and in correlation with the rapid population growth, its demand is escalating. The issues associated with fossil fuels, their depletion, and negative environmental effects have led to the exploration of alternative energy sources. Biofuels such as biodiesel and bioethanol have emerged as promising, renewable, and environmentally friendly alternatives. This study explores the sustainable production of bioethanol from Citrus peels and biodiesel from Pumpkin seed oil, assessing their potential contributions to energy efficiency and societal benefits. Citrus peels, underwent acid hydrolysis (0.5% H₂SO₄, 2 h) to release fermentable sugars, followed by anaerobic fermentation using 10% (v/v) Saccharomyces cerevisiaea. The resulting bioethanol was confirmed through qualitative analysis via Jones reagent. GC-MS of the hydrodistilled Citrus peel revealed 90.53% limonene in Citrus oil Biodiesel was produced via transesterification of pumpkin seed oil with methanol and potassium hydroxide (KOH) catalyst. GC-MS identified 65.9% unsaturated fatty acids (linoleic and oleic acids dominant), with a 97.5% yield, 0.7% ash content, and calorific value of 39,586 kJ/kg, meeting ASTM/EN standards. The study highlights the potential of utilizing agricultural waste and by-products in biofuel production, contributing to a circular economy and reducing environmental impact. The study demonstrates the viability of Citrus peel waste and Pumpkin seed oil as feedstocks, reducing reliance on fossil fuels while valorizing agricultural by-products. Challenges in scaling production require further exploration to maximize societal and environmental benefits, particularly in resource-rich regions.

Keywords

Energy , Citrus peels , Pumpkin seeds , Biodiesel , bioethanol

References

• Adams, R. P., 2007. Identification of essential oil components by gas chromatography/mass spectorscopy. Allured Pub. Corp.
• Agu, R. C., Amadife, A. E., Ude, C. M., Onyia, A., Ogu, E. O., Okafor, M., & Ezejiofor, E. (1997). Combined heat treatment and acid hydrolysis of cassava grate waste (CGW) biomass for ethanol production. Waste Management, 17, 91–96. https://doi.org/10.1016/S0956-053X(97)00027-5
• Ahmad, A., Rahmad, Rita, N., & Noorjannah, L. (2022). Effect of acid hydrolysis on bioethanol production from oil palm fruit bunches. Materials Today: Proceedings, 63, S276–S281. https://doi.org/10.1016/J.MATPR.2022.02.461
• Ahtesham, S. A., & Hebbal, O. (2020). Pumpkin seed oil biodiesel an alternate fuel to diesel: A review. International Research Journal of Engineering and Technology, 7(10), 700–707. www.irjet.net
• Akaracharanya, A., Kesornsit, J., Leepipatpiboon, N., Srinorakutara, T., Kitpreechavanich, V., & Tolieng, V. (2011). Evaluation of the waste from cassava starch production as a substrate for ethanol fermentation by Saccharomyces cerevisiae. Annals of Microbiology, 61, 431–436. https://doi.org/10.1007/S13213-010-0155-8
• Ayala, J. R., Montero, G., Coronado, M. A., García, C., Curiel-Alvarez, M. A., León, J. A., Sagaste, C. A., & Montes, D. G. (2021). Characterization of orange peel waste and valorization to obtain reducing sugars. Molecules, 26(5), 1348. https://doi.org/10.3390/MOLECULES26051348
• Brown, S. W., Oliver, S. G., Harrison, D. E. F., & Righelato, R. C. (1981). Ethanol inhibition of yeast growth and fermentation: Differences in the magnitude and complexity of the effect. European Journal of Applied Microbiology and Biotechnology, 11, 151–155. https://doi.org/10.1007/BF00511253/METRICS
• Caputi, A., Ueda, M., & Brown, T. (1968). Spectrophotometric determination of ethanol in wine. American Journal of Enology and Viticulture, 19, 160–165. https://doi.org/10.5344/AJEV.1968.19.3.160
• Castro, R. C. de A., & Roberto, I. C. (2015). Effect of nutrient supplementation on ethanol production in different strategies of saccharification and fermentation from acid-pretreated rice straw. Biomass Bioenergy, 78, 156–163. https://doi.org/10.1016/J.BIOMBIOE.2015.04.019
• Cheng, N., Koda, K., Tamai, Y., Yamamoto, Y., Takasuka, T. E., & Uraki, Y. (2017). Optimization of simultaneous saccharification and fermentation conditions with amphipathic lignin derivatives for concentrated bioethanol production. Bioresource Technology, 232, 126–132. https://doi.org/10.1016/J.BIORTECH.2017.02.018
• Correa, D. F., Beyer, H. L., Fargione, J. E., Hill, J. D., Possingham, H. P., Thomas-Hall, S. R., & Schenk, P. M. (2019). Towards the implementation of sustainable biofuel production systems. Renewable and Sustainable Energy Reviews, 107, 250–263. https://doi.org/10.1016/J.RSER.2019.03.005
• D240 Standard Test Method for Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter. (2019.). Retrieved August 8, 2024, from https://www.astm.org/d0240-19.html
• D482 Standard Test Method for Ash from Petroleum Products. (2019.). Retrieved August 8, 2024, from https://www.astm.org/d0482-19.html
• Eleiwa, N. Z. H., Bakr, R. O., & Mohamed, S. A. (2014). Phytochemical and Pharmacological Screening of Seeds and Fruits Pulp of Cucurbita moschata Duchesne Cultivated in Egypt. International Journal of Pharmacognosy and Phytochemistry, 29, 12261–1236. https://doi.org/10.12817/20517858.29.1.27703371
• Ezema, B. O., Omeje, K. O., Ozioko, J. N., Fernandez-Castane, A., Oscar O., & Eze, S. (2023). Biodiesel potential of Cucumeropsis mannii (white melon) seed oil: A neglected and underutilized resource in Nigeria. Heliyon, 9, e16799. https://doi.org/10.1016/J.HELIYON.2023.E16799
• Ezzat, S. M., Adel, R., & Abdel-Sattar, E. (2022). Pumpkin Bio-Wastes as Source of Functional Ingredients. Mediterranean Fruits Bio-wastes: Chemistry, Functionality and Technological Applications, 667–696. https://doi.org/10.1007/978-3-030-84436-3_29
• Hagos, M., Yaya, E. E., Chandravanshi, B. S., & Redi-Abshiro, M. (2023). Determination of fatty acids composition by GC-MS and physicochemical parameters of pumpkin (Cucurbita maxima) seed oil cultivated in Ethiopia. Bulletin of the Chemical Society of Ethiopia, 37(3), 565–577. https://doi.org/10.4314/BCSE.V37I3.3
• Hardjono, H., Dewi, E. N., Lusiani, C. E., Febriansyah, I., & Bachtiar, R. I. (2021). D-limonene from orange (Citrus Maxima) peel extraction as destructive agent of styrofoam waste. IOP Conference Series: Materials Science and Engineering, 1073(1), 012013. https://doi.org/10.1088/1757-899X/1073/1/012013
• Hu, R., Lin, L., Liu, T., Ouyang, P., He, B., & Liu, S. (2008). Reducing Sugar Content in Hemicellulose Hydrolysate by DNS Method: A Revisit. Journal of Biobased Materials and Bioenergy, 2(2), 156–161.https://doi.org/10.1166/JBMB.2008.306
• Hussain, A., Kausar, T., Sehar, S., Sarwar, A., Quddoos, M. Y., Aslam, J., Liaqat, A., Siddique, T., An, Q. U., Kauser, S., Rehman, A., & Nisar, R. (2023). A review on biochemical constituents of pumpkin and their role as pharma foods; a key strategy to improve health in post COVID 19 period. Food Production, Processing and Nutrition, 5(1). https://doi.org/10.1186/S43014-023-00138-Z
• Kant Bhatia, S., Kant Bhatia, R., Jeon, J. M., Pugazhendhi, A., Kumar Awasthi, M., Kumar, D., Kumar, G., Yoon, J. J., & Yang, Y. H. (2021). An overview on advancements in biobased transesterification methods for biodiesel production: Oil resources, extraction, biocatalysts, and process intensification technologies. Fuel, 285, 119117. https://doi.org/10.1016/J.FUEL.2020.119117
• Knothe, G., & Razon, L. F. (2017). Biodiesel fuels. Progress in Energy and Combustion Science, 58, 36–59. https://doi.org/10.1016/J.PECS.2016.08.001
• Lam, M. K., & Lee, K.T. (2011). Production of biodiesel using palm oil. In: Pandey, A., Larroche, C., Ricke, S.C., Dussap, C. & Gnansounou, E. (eds) Biofuels: Alternative Feedstocks and Conversion Processes, 353–374. https://doi.org/10.1016/B978-0-12-385099-7.00016-4
• Li, Y., Fabiano-Tixier, A.-S., & Chemat, F. (2014). Essential Oils as Reagents in Green Chemistry. SpringerBriefs in Molecular Science. https://doi.org/10.1007/978-3-319-08449-7
• Mahato, N., Sharma, K., Sinha, M., Dhyani, A., Pathak, B., Jang, H., Park, S., Pashikanti, S., & Cho, S. (2021). Biotransformation of Citrus waste-I: Production of biofuel and valuable compounds by fermentation. Processes, 9, 220 -229, https://doi.org/10.3390/PR9020220
• Manakas, P., Balafoutis, A.T., Kottaridi, C., & Vlysidis, A. (2024). Sustainability assessment of orange peel waste valorization pathways from juice industries. Biomass Conversion and Biorefinery, 1–20. https://doi.org/10.1007/S13399-024-05626-X/FIGURES/6
• Medina, J. D. C., Jr, A. I. M., & Medina, J. D. C., Jr, A.I.M. (2020). Ethanol production, current facts, future scenarios, and techno-economic assessment of different biorefinery configurations. Bioethanol Technologies. https://doi.org/10.5772/INTECHOPEN.95081
• Moser, B.R. (2009). Biodiesel production, properties, and feedstocks. In Vitro Cellular & Developmental Biology – Plant, 45(3), 229–266. https://doi.org/10.1007/S11627-009-9204-Z
• Muhammad, G., Alam, M. A., Mofijur, M., Jahirul, M. I., Lv, Y., Xiong, W., Ong, H. C., & Xu, J., (2021). Modern developmental aspects in the field of economical harvesting and biodiesel production from microalgae biomass. Renewable and Sustainable Energy Reviews, 135, 110209. https://doi.org/10.1016/J.RSER.2020.110209
• Nader, J., Allaf, T., & Allaf, K. (2022). Instant Controlled Pressure Drop (DIC) as an Emerging Food Processing Technology. In: Gavahian, M. (eds) Emerging Food Processing Technologies. Methods and Protocols in Food Science . Humana, New York, NY. 229–246. https://doi.org/10.1007/978-1-0716-2136-3_16
• Rapier, R. (2024). Breaking Records: 2024 Statistical Review Of World Energy Highlights. Forbes. https://www.forbes.com/sites/rrapier/2024/06/22/breaking-records-2024-statistical-review-of-world-energy-highlights/.
• Samaras, C. (2019). Wasting less electricity before use. Nature Climate Change, 9, 648–649. https://doi.org/10.1038/s41558-019-0558-x
• Schinas, P., Karavalakis, G., Davaris, C., Anastopoulos, G., Karonis, D., Zannikos, F., Stournas, S., & Lois, E. (2009). Pumpkin (Cucurbita pepo L.) seed oil as an alternative feedstock for the production of biodiesel in Greece. Biomass Bioenergy, 33, 44–49. https://doi.org/10.1016/J.BIOMBIOE.2008.04.008
• Somda, M. K., Savadogo, A., Ouattara, C. A. T., Ouattara, A. S., & Traore, A.S. (2010). Thermotolerant and alcohol-tolerant yeasts targeted to optimize hydrolyzation from mango peel for high bioethanol production. Asian Journal of Biotechnology, 3, 77–83. https://doi.org/10.3923/AJBKR.2011.77.83
• Suri, S., Singh, A., & Nema, P.K. (2022). Current applications of citrus fruit processing waste: A scientific outlook. Applied Food Research 2, 100050. https://doi.org/10.1016/J.AFRES.2022.100050
• Teke, G. M., De Vos, L., Smith, I., Kleyn, T., & Mapholi, Z. (2023). Development of an ultrasound-assisted pre-treatment strategy for the extraction of d-Limonene toward the production of bioethanol from citrus peel waste (CPW). Bioprocess. Biosyst. Eng., 46, 1627–1637. https://doi.org/10.1007/S00449-023-02924-Y/TABLES/4
• Tse, T. J., Wiens, D.J ., Chicilo, F., Purdy, S. K., & Reaney, M. J. T. (2021). value-added products from ethanol fermentation—a review. Fermentation, 7, 267-273. https://doi.org/10.3390/FERMENTATION7040267
• Wilkins, M. R., Widmer, W. W., & Grohmann, K. (2007). Simultaneous saccharification and fermentation of citrus peel waste by Saccharomyces cerevisiae to produce ethanol. Process Biochemistry, 42, 1614–1619. https://doi.org/10.1016/J.PROCBIO.2007.09.006