From Waste to Fuel: An Integrated Workflow for Biodiesel Synthesis from Waste Cooking Oil Using Eggshell-Derived CaO Catalyst

Abstract:

In this study, biodiesel was produced through the catalytic conversion of waste cooking oil into fatty acid methyl esters using methanol and calcium oxide derived from calcined eggshells as a heterogeneous catalyst. Different factors affecting reaction performance, including feedstock addition method, the molar ratio of methanol to waste cooking oil, catalyst loading, reaction time, and reaction temperature, were systematically studied. The results showed a biodiesel yield of 90% under optimal conditions: a feedstock addition time of 2 hours, a methanol-to-waste cooking oil weight ratio of 10:1, a catalyst loading of 7% based on the weight of the oil feedstock, a reaction time of 5 hours, and a reaction temperature of 60 °C. The CaO catalyst was successfully reused three times, with only a minor loss of activity. Complete conversion of waste cooking oil to biodiesel was confirmed by TLC, using a solvent system with a 15:1 volume ratio of petroleum ether to ethyl acetate. Column chromatography with the same solvent system was used for further purification. FT-IR analysis confirmed the successful transesterification, as evidenced by spectral changes associated with the formation of methyl esters. GC-MS identified various fatty acid methyl esters, providing insights into the composition and confirming product quality. Additionally, in laboratory-scale tests, selected fuel properties, including density, viscosity, flash point, copper chip corrosion, and water content, were measured. The results indicate that biodiesel has characteristics similar to those of conventional diesel and commercial biodiesel, supporting its potential as a renewable energy resource.

• Periodical: Engineering Headway (Volume 40)
• Pages: 151-164
• DOI: https://doi.org/10.4028/p-9kfH1H
• Online since: July 2026
• Authors: Tong Thi Minh Thu*, Vo Nhi Kieu, Tong Thi Kim Oanh
• Keywords: Biodiesel, Biofuel, Heterogeneous Catalyst, Transesterification, Waste Cooking Oil

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