Biodiesel production from waste cooking oil using calcium oxide derived from scallop shell waste

Abstract Biodiesel is one of the alternative forms of diesel fuel and can be obtained using the transesterification process of waste cooking oil with a catalyst to accelerate the reaction. The heterogeneous catalyst from waste scallop shells is used due to its potential for being reused in the subsequent transesterification reactions. Heterogeneous catalysts can also be recycled, contributing to their environmentally friendly nature. This study aims to identify the performance of recycling a calcium oxide (CaO) catalyst from scallop shell waste on synthesis biodiesel. The method used is the transesterification method with the basic ingredients of waste cooking oil using a CaO catalyst. Then, after the transesterification process is complete, the catalyst is separated from the biodiesel and recycled to be reused in the transesterification process up to five times. The biodiesel samples obtained are identified for yield value, physico-chemical properties, thermal properties and performance. X-ray diffraction characterization results for the CaO catalyst show that it has a crystal size of 67.83 nm. Scanning electron microscope characterization shows that it has spherical particle shapes. Fourier transform infrared characterization shows the presence of Ca–O bonds. The highest biodiesel yield value of 74.23% is obtained in biodiesel Cycle 1. The flash point value of biodiesel samples ranges from 141.2°C to 149°C. Further, all of the biodiesel samples exhibit a cetane number of 75. The highest lower heating value of 38.22 MJ/kg is obtained in biodiesel Cycle 1 and the viscosity of the biodiesel samples ranges from 5.65 to 5.88 cSt. The density of the biodiesel samples ranges from 881.23 to 882.92 kg/m3. Besides, ester functional groups (C=O) and methyl functional groups have been successfully formed in all samples, with the methyl oleate compound observed as dominating the biodiesel samples. The cloud point value of the biodiesel samples ranges from 12°C to 13°C, and their pour point value ranges from 10°C to 12°C. The lead content in biodiesel is 0.8826 mg/kg. The lowest sulphur content is obtained from biodiesel Cycles 1 and 2 at 0.005%. Performance tests show that biodiesel has lower torque and brake power values than commercial diesel fuel and higher specific fuel consumption values than commercial diesel fuel. Biodiesel is synthesized from waste cooking oil using transesterification catalysed by CaO from scallop shell waste. After the process is complete,