Sustainable production of biodiesel from microalgae by direct transesterification

This study addresses the question of the sustainable production of biodiesel (fatty acid ethyl esters) by direct transesterification from Chlorella sp. The lipid fractions from Chlorella sp. using chloroform: methanol, methanol, and ethanol were obtained and the acid value measurements were 39.4, 58.2, and 82.5 mg KOH/g, respectively. Following this, transesterification of algal lipid extraction and direct transesterification was undertaken in the presence of ethanol and the results were compared with those for methanol. Apart from the lower yield in extracted lipids obtained with ethanol, when ethanol was used for transesterification of the algal lipid extraction, surprisingly, similar yields of fatty acid ethyl esters and fatty acid methyl esters were obtained. Furthermore, direct transesterification from Chlorella sp. provided higher ethyl and methyl esters yields than was the case with the extraction-transesterification process. Ethanol, a renewable feedstock, is the most sustainable alternative, which, compared to methanol in direct transesterification, resulted in similar fatty acid methyl and ethyl ester yields (11.6% and 11.0%, respectively, in the same experimental conditions). (C) 2016 Elsevier B.V. All rights reserved.