Biodiesel Preparation by Optimization of Rubber Seed In Situ Esterification

Jalil, Fatah Abdul; Asif, Khairun; Prabaningrum, Nunung; Kusnanto, Kusnanto

doi:10.30501/jree.2026.499402.2232

Biodiesel Preparation by Optimization of Rubber Seed In Situ Esterification

Document Type : Research Article

Authors

Fatah Abdul Jalil

Khairun Asif

Nunung Prabaningrum

Kusnanto Kusnanto

Department of Nuclear Engineering and Engineering Physics, Faculty of Engineering, Universitas Gadjah Mada, Jalan Grafika 2 Yogyakarta, 55284, Indonesia.

10.30501/jree.2026.499402.2232

Abstract

Optimization of the in situ esterification of rubber seed was investigated in a batch process. Rubber seed is a non-edible seed containing a high vegetable oil content (54.64 ± 1.80%), and therefore, it does not compete with the food sector. The oil in rubber seeds, however, contains a substantial level of free fatty acids, approximately 10.4%. The oil recovery processing step can be reduced by applying in situ esterification. The use of n-hexane as a cosolvent can facilitate oil extraction. Consequently, in situ methanolysis-esterification of rubber seed with n-hexane as a cosolvent was employed to produce a high-yield, low-acid-number methyl ester, which was optimized using a central composite design of the response surface method. The acid number was determined by AOCS Cd 3d-63 titration, and the methyl ester composition was verified using Gas Chromatography-Mass Spectrometry analysis. Optimization of rubber seed in situ esterification resulted in a maximum yield of 89.92 ± 0.99% and a low acid number of 0.45 mg KOH/g at a solution volume of methanol and n-hexane to rubber seed mass ratio of 7:1 mL/g, a methanol volume fraction of 0.44 in the blended methanol-n-hexane solution, and 12.37 wt.% H2SO4 for a reaction time of 5 hours. The methyl ester yield increased and the acid number decreased with increasing reaction time up to 5 hours. Beyond this duration, extending the reaction time did not significantly enhance the methyl ester yield or reduce the acid number. The obtained methyl ester properties complied with the SNI-7182 standard.

Graphical Abstract

Keywords

In-situ Esterification

Methyl Ester

Biodiesel

Rubber Seed

Acid Number

Yield

Central Composite Design

N-hexane Cosolvent

Subjects

Biomass and Bioenergy

1. Abdulkadir, B.A., Danbature, W.,Yirankinyuki, F.Y., Magaji, B., & Muzakkir, M.M. (2014). In Situ Transesterification of Rubber Seeds (Hevea brasiliensis). Greener Journal of Physical Sciences, 4(3), 038-044. https://gjournals.org/GJPS/archive/vol-43-april-2014/bashir-et-al.html

2. Abdulkadir, B.A., Uemura, Y., Ramli, A., Osman, N., Kusakabe, K., & Kai, T. (2015). Production of Biodiesel from Rubber Seeds (Hevea Brasiliensis) by In situ Transesterification Method. Journal of Japan Institute of Energy, 94(7), 763-768, https://doi.org/10.3775/jie.94.763

3. Adenuga, A.A., Idowu, O.O, & Oyekunle, J.A.O. (2020). Synthesis of quality biodiesel from Calophyllum inophyllum kernels through reactive extraction method: Optimization of process parameters and characterization of the products. Renewable Energy, 145, 2530-2537. https://doi.org/10.1016/j.renene.2019.08.035

4. Ahmed, M., Abdullah, A., Patle, D.S., Shahadat, M., Ahmad, Z., Aslam, M., & Vo, D. V. N. (2022). Feedstocks, catalysts, process variables and techniques for biodiesel production by one‐pot extraction‐transesterification: a review. Environmental Chemistry Letters, 20, 335–378. https://doi.org/10.1007/s10311-021-01358-w

5. Al-Humairi, S.T., Lee, J.G.M., Salihu, M., & Harvey, A.P. (2022). Biodiesel Production through Acid Catalyst In Situ Reactive Extraction of Chlorella vulgaris Foamate. Energies, 15, 4482. https://doi.org/10.3390/en15124482

6. Arumugam, A., Thulasidharan, D., & Jegadeesan, G.B. (2018). Process optimization of biodiesel production from Hevea brasiliensis oil using lipase immobilized on spherical silica aerogel. Renewable Energy, 116, 755-761. https://doi.org/10.1016/j.renene.2017.10.021

7. Budiastuti, H., Hanifah, N.A., Mardiani, D.U., Haryadi, Rusdianasari, & Fudholi, A. (2022). Biodiesel Production from Rubber Seed Oil as Alternative Energy Source – A Review. International Journal of Applied Technology Research, 3(2), 120-134. https://doi.org/10.35313/ijatr.v3i2.92

8. Dhawane, S.H., Kumar, T., & Halder , G. (2015). Central composite design approach towards optimization of flamboyant pods derived steam activated carbon for its use as heterogeneous catalyst in transesterification of Hevea brasiliensis oil. Energy Conversion and Management, 100, 277–287. http://dx.doi.org/10.1016/j.enconman.2015.04.083

9. Dhawane, S. H., Kumar, T., & Halder, G. (2018). Process optimisation and parametric effects on synthesis of lipase immobilised carbonaceous catalyst for conversion of rubber seed oil to biodiesel. Energy Conversion and Management, 176, 55-68. https://doi.org/10.1016/j.renene.2016.12.096

10. Gimbun, J., Ali, S., Kanwal, C. C. S. C., Shah, L., A., Ghazali, N.H.M., Cheng, C., K., & Nurdin, S. (2013). Biodiesel Production From Rubber Seed Oil Using Activated Cement Clinker As Catalyst. Procedia Engineering, 53, 13-19. https://doi.org/10.1016/j.proeng.2013.02.003

11. Gomaa, M.A, Gombocz, N., Schild, D., Mjalli, F.S., Al-Harrasi, A., & Abed, R.M.M. (2021). Effect of organic solvents and acidic catalysts on biodiesel yields from primary sewage sludge, and characterization of fuel properties. Biofuels, 12(4), 405-413. https://doi.org/10.1080/17597269.2018.1479137

12. Ibrahim, H. D., Siswanto, D., Saefulhak, Y., Suharyati, Pratiwi, N. I., Pambudi, S. H., Wibowo, J. L., Arifin, F. D., Sauqi, A., Damanik, J. T., Pangaribuan, D. B. T., & Kristanto, N. (2022). Indonesia Energy Outlook 2022. Bureau of Energy Policy and Assembly Facilitation Secretariate General of The National Energy Council. https://www.scribd.com/document/656333181/Buku-Energi-Outlook-2022-Versi-Bhs-Inggris

13. Ikwuagwu, O.E., Ononogbu, I.C., & Njoku, O.U. (2000). Production of biodiesel using rubber [Hevea brasiliensis (Kunth. Muell.)] seed oil. Industrial Crops and Products, 12, 57-62. https://doi.org/10.1016/S0926-6690(99)00068-0

14. Jain, S. (2023). Biodiesel production from food waste using in situ transesterification method. Sustainable Energy Technologies and Assessments, 58, 103380. https://doi.org/10.1016/j.seta.2023.103380

15. Jain, S. (2026). Optimized In-Situ Transesterification of Spirogyra Using KOH-Activated Wheat Straw Biochar Catalyst. Results in Engineering, 29. https://doi.org/10.1016/j.rineng.2025.108896

16. Khazaai, S. N. M., Maniama, G. P., Rahima, M. H. A., Yusoff, M. M., & Matsumura, Y. (2017). Review on methyl ester production from inedible rubber seed oil under various catalysts. Industrial Crops and Products, 97, 191-195. https://doi.org/10.1016/j.indcrop.2016.11.052

17. Lakshmi, S.B.A.V.S., Pillai, N.S., Mohamed, M.S.B.K., & Narayanan, A. (2020). Biodiesel production from rubber seed oil using calcined eggshells impregnated with Al2O3 as heterogeneous catalyst: A comparative study of RSM and ANN optimization. Brazilian Journal of Chemical Engineering, 37, 351–368. https://doi.org/10.1007/s43153-020-00027-9

18. Lüneburger, S., Gallina, A. L., Soares, L. C., & Benvegnú, D., M. (2022). Biodiesel production from Hevea Brasiliensis seed oil. Fuel, 324, 124639. https://doi.org/10.1016/j.fuel.2022.124639

19. Mani, Y., Devaraj, T., Devaraj, K., AbdurRawoof, S.A., & Subramanian, S. (2020). Experimental investigation of biodiesel production from Madhuca longifolia seed through in situ transesterification and its kinetics and thermodynamic studies. Environmental Science and Pollution Research, 27, 36450-36462. https://doi.org/10.1007/s11356-020-09626-y

20. Milano, J., Ong, M.Y., Tiong, S.K., Ideris, F., Silitonga, A.S., Sebayang, A.H., Tana, C.H., Fattah, I.M.R., Fonad, Z., & Hossaine, N. (2025). A comparative study of the production of methyl esters from non-edible oils as potential feedstocks: Process optimization and two-step biodiesel characterization. Results in Engineering, 25, 104285. https://doi.org/10.1016/j.rineng.2025.104285

21. Myers, R. H., & Montgomery, D. C. (2009). Response Surface Methodology: Process and Product Optimization Using Designed Experiments. Third Edition. A Wiley-Interscience Publication. John Wiley & Sons, INC. New York. https://books.google.co.id/books?id=YFSzCgAAQBAJ

22. Oladipoa, B., & Betiku, E. (2020). Optimization and kinetic studies on conversion of rubber seed (Hevea brasiliensis) oil to methyl esters over a green biowaste catalyst. Journal of Environmental Management, 268, 110705. https://doi.org/10.1016/j.jenvman.2020.110705

23. Othman, M. F., Adam, A., Najafi, G., & Mamat, R. (2017). Green fuel as alternative fuel for diesel engine: A review. Renewable and Sustainable Energy Reviews, 80, 694-709. https://doi.org/10.1016/j.rser.2017.05.140

24. Oyekunle, D.T., Gendy, E.A., Barasa, M., Oyekunle, D.O., Oni, B., & Tiong, S.K. (2024). Review on utilization of rubber seed oil for biodiesel production: Oil extraction, biodiesel conversion, merits, and challenges. Cleaner Engineering and Technology, 21, 100773. https://doi.org/10.1016/j.clet.2024.100773

25. Parthiban, K.S., Pandian, S., & Subramanian, D. (2021). Conventional and in-situ transesterification of Annona squamosa seed oil for biodiesel production: Performance and emission analysis. Environmental Technology & Innovation, 23, 101593. https://doi.org/10.1016/j.eti.2021.101593

26. Pereira, S.A., dos Santos, S.B.F., Arruda, T.B.M.G., Ferreira, E.N., Chaves, P.O.B., de Oliveira, D.L.V., de Almeida Sousa, J.E., Rodrigues, F.E.A., & Ricardo, N.M.P.S. (2023). In situ transesterification of the catole coconut (Syagrus Cearensis) utilizing experimental design by Taguchi method. Industrial Crops & Products, 205, 117490. https://doi.org/10.1016/j.indcrop.2023.117490

27. Rahman, W.U., Khan, A.M., Anwer, A.H., Hasan, U., Karmakar, B., & Halder, G. (2022). Parametric optimization of calcined and Zn-doped waste egg-shell catalyzed biodiesel synthesis from Hevea brasiliensis oil. Energy Nexus, 6, 100073. https://doi.org/10.1016/j.nexus.2022.100073

28. Ridwan I., Budiastuti, H., Indarti R., Wahyuni N. L. E., Safitri, H. M., & Ramadhan, R. L. (2023). The optimization of tetrahydrofuran as a co-solvent on biodiesel production from rubber seeds using response surface methodology. Materials Science for Energy Technologies, 6, 15-20. https://doi.org/10.1016/j.mset.2022.11.002

29. 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(3), 2970-2992. https://doi.org/10.1016/j.rser.2017.10.037

30. Samart, C., Karnjanakom, S., Chaiya, C., Reubroycharoen, P., Sawangkeaw, R., & Charoenpanich, M. (2019). Statistical optimization of biodiesel production from para rubber seed oil by SO3H-MCM-41 catalyst. Arabian Journal of Chemistry, 12, 2028–2036. https://doi.org/10.1016/j.arabjc.2014.12.034

31. Sugebo, B., Demrew, Z., Feleke, S., & Biazen, M. (2021). Evaluation and characterization of rubber seed oil for biodiesel production. Biomass Conversion and Biorefinery, 15, 22125–22135. https://doi.org/10.1007/s13399-021-01900-4

32. Thakkar, K., Shah, K., Kodgire, P., & Kachhwaha, S.S. (2019). In-situ reactive extraction of castor seeds for biodiesel production using the T coordinated ultrasound–microwave irradiation: Process optimization and kinetic modeling. Ultrasonics–Sonochemistry, 50, 6–14. https://doi.org/10.1016/j.ultsonch.2018.08.007

33. Thanh, N.T., Mostapha, M., Lama, M.K., Ishak, S., Dasan, Y.K., Lim, J.W., Tan, I.S., Lau, S.Y., Chin, B.L.F., & Hadibarata, T. (2022). Fundamental understanding of in-situ transesterification of microalgae biomass to biodiesel: A critical review. Energy Conversion and Management, 270, 116212. https://doi.org/10.1016/j.enconman.2022.116212

34. Widayat, Wibowo, A. D. K., & Hadiyanto. (2013). Study on production process of biodiesel from rubber seed (hevea brasiliensis) by in situ (trans)esterification method with acid catalyst. Energy Procedia, 32, 64-73. https://doi.org/10.1016/j.egypro.2013.05.009

35. Zamberia, M.M., Ani, F.N., & Abdollah, M.F. (2016). Heterogeneous Transesterification Of Rubber Seed Oil Biodiesel Production. Jurnal Teknologi (Sciences & Engineering), 78: 6–10, 115–110. https://journals.utm.my/jurnalteknologi/article/view/9196/5484

36. Zhu, Y., Xu, J., Li, Q., & Mortimer, P. E. (2014). Investigation of rubber seed yield in Xishuangbanna and estimation of rubber seed oil based biodiesel potential in Southeast Asia. Energy, 69. 837-842. https://doi.org/10.1016/j.energy.2014.03.079