Advances in Heterogeneous and Enzymatic Catalysis for the Industrial Production of Biodiesel by Transesterification: An Overview

Biodiesel fuels (BDFs) have emerged as environmentally friendly substitutes for the fossil fuels being used extensively today. BDFs are essentially methyl esters of fatty acids and are produced by a reaction called as transesterification using catalysts. Alkali catalysis is widely applied for biodiesel production but suffers from certain drawbacks such as high energy consumption, difficulty in the transesterification of triglycerides with a high free fatty acid content and additional costs arising from downstream processes like glycerol recovery, treatment of highly alkaline waste water, etc. Enzymatic catalysis allows for the synthesis of specific alkyl esters, easy recovery of glycerol and the transesterification of triglycerides with high free fatty acid content but is impeded by the high cost of lipase enzyme. Enzyme immobilization, whole-cell biocatalysis, novel lipase expressing yeast cells and recombinant fungi are the approaches that are being used to reduce enzyme associated process costs for industrial scale production of biodiesel.