Latest advances in degumming feedstock oils for large-scale biodiesel production

Abstract

The removal of gummy or mucilaginous substances from vegetable oils, commonly known as degumming, is required for the use of crude vegetable oils as the feedstock for biodiesel production. These gums reduce the rate of transesterification reactions by deactivation of the catalyst and they hinder the separation of the glycerol phase from the biodiesel. They also cause the deposition of carbon particles within engine machinery and affect performance. To take care of these issues, gums should be separated from the oils to make the oils suitable for use as fuel. Chemical treatment, membrane separation, and biological separation processes have been reported in the literature for this purpose. In the chemical treatment process aqueous solutions of chemicals like acids, bases, ethylenediaminetetraacetic acid (EDTA), and water are used for separating gums. The membrane separation process is based on size exclusion, and polymeric, ceramic, and inorganic membranes are used to separate gums from oil. In biological degumming, phospholipase groups of enzymes are used. These enzymes hydrolyze gums into fatty acids and lipophilic substances. Enzyme degumming also enhances oil-phase yield. This paper reviews the chemical nature of gums and presents a comprehensive critical summary of different degumming technologies, their specific features, effecting parameters, advantages and disadvantages, and industrial uses.