Biodiesel Production from Waste Frying Oil using Catalysts Derived from Waste Materials

Abstract

Domestic resources such as vegetable oil, animal fats, tallows, and waste frying oil are common raw materials for making biodiesel. In contrast to ordinary diesel, biodiesel helps to reduce CO2 emissions. This study aimed to produce biodiesel using waste frying oil in the presence of suitable solid waste-derived heterogeneous catalysts. Firstly, CaO/K2O catalyst was synthesised using eggshells and banana peels. Then, the pre-prepared catalyst (CaO/K2O) modified with ZnO was utilized for biodiesel production. The prepared catalyst and biodiesel were characterized using X-ray diffraction (XRD) and FTIR spectroscopy. The AOAC and ASTM standard methods were employed to analyze the physicochemical properties of oils and biodiesel. The catalytic efficiency of CaO/K2O and CaO/K2O-ZnO tested for the transesterification of purified oil to biodiesel at the catalyst weight (1-7 %wt), temperature (60-80°C), and methanol to oil ratios ranging from 3:1 to 12:1. The highest biodiesel yield (92%) obtained when 5 %wt CaO/K2O catalyst used. However, a 95% yield resulted when using a 3 %wt CaO/K2O-ZnO catalyst load in 2 h with a methanol to oil (v/v) ratio of 9:1 at 65°C. The study revealed that waste frying oil is a good source of biodiesel which could replace nonrenewable energy in the future. The catalysts made from solid waste could also replace an expensive chemical catalyst.