Abstract
Biodiesel synthesis processes including pyrolysis, direct blending, transesterification, and advanced technologies such as microwave- and ultrasound-assisted and supercritical processes from palm oil mill effluent (POME) are reviewed to highlight the significance and advances in terms of process sustainability and cost. POME as the most contaminated waste can be effectively utilized for biodiesel production. Supercritical transesterification offers more advantages over the other processes including higher reaction rate, without catalyst constraint, producing pure glycerol, and simple product separation process. The addition of co-solvents like CO2 should be investigated for supercritical biodiesel production from POME. Although POME is an inexpensive source to synthesize biodiesel, innovative processes are needed to maximize the oil recovery from POME. Optimization of transesterification parameters is required for high production yields and sustainable processing.