A comprehensive review of the production methods and effect of parameters for glycerol-free biodiesel production

Abstract

This review appraises the latest scientific progress and the accomplishments of interesterification technology as an alternative to conventional transesterification reaction. The merits and limitations of various types of catalytic techniques as well as non-catalytic supercritical glycerol-free processes have been elucidated with a comprehensive comparison. Contrary to the cheap price of glycerol, the higher-revenue by-products, triacetin and glycerol carbonate, will boost the gross profit margin of biodiesel production. The influences of reaction parameters such as reactant ratio, catalyst loading, reaction time, temperature, and co-solvent addition are also addressed. According to the latest research, the alkali-catalyzed and non-catalytic supercritical interesterifications are preferable due to higher yield. Methyl acetate, ethyl acetate and dimethyl carbonate do not inhibit lipase activity, unlike typical alcohols. Acidic catalysis may be the way forward to resolve the extreme operating conditions of non-catalytic supercritical interesterification, high cost of enzymes and manage waste feedstocks with high free fatty acid and water contents under moderate conditions. Currently, the majority of interesterification reactions were undertaken on laboratory size, whereas just a handful was evaluated on a pilot scale. A continuous research in interesterification technology is necessary by conducting a thorough investigation of the feasibility of state-of-the-art technology to engage a wide array of feedstocks. Future study should also concentrate on microbes and agricultural waste as a sustainable route for energy recovery from renewable feedstocks.