Evaluation of Shell-Derived Calcium Oxide Catalysts for the Production of Biodiesel Esters from Cooking Oils

Due to the high cost of feedstock and catalyst in biodiesel production, the viability of the biodiesel industry has been dependent on government subsidies or tax incentives. In order to reduce the cost of production, food wastes including eggshells and oyster shells have been used to prepare calcium oxide (CaO) catalysts for the transesterification reaction of biodiesel synthesis. The shells were calcined at 1000 °C for 4 hours to obtain CaO powders which were investigated as catalysts for the transesterification of waste cooking oil. The catalysts were characterized by Fourier Transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and X-ray fluorescence (XRF) spectroscopy. Reaction parameters such as methanol-to-oil molar ratio, CaO catalyst concentration, and reaction time were evaluated and optimized for the percentage conversion of cooking oil to biodiesel esters. The oyster-based CaO showed better catalytic activity when compared to the eggshell-based CaO under the same set of reaction conditions.