Biodiesel production from microalgal oil extracted by acid-catalyzed hot water treatment

Biodiesel, a renewable alternative diesel fuel, is produced mainly from vegetable oils and, sometimes, animal fats. Recently, a great deal of research effort has been devoted to biodiesel production that utilizes microalgae as an oil source, given that some microalgae show higher oil productivity than plant oils. Microalgae offer the additional advantage of not competing with food crops and utilizing carbon dioxide and wastewater. Conversion of microalgae to biodiesel typically includes the following four steps: microalgae cultivation, cell harvesting, oil extraction, and biodiesel conversion. During cell harvesting, water is removed from microalgae. Because the extraction of microalgal oil from dried microalgae gives the high costs incurred in the dewatering process, wet extraction has emerged an attractive alternative approach. To enhance the oil extraction yield from wet microalgae, acid-catalyzed hot water treatment can be applied. In this study, microalgal oil was extracted from mixed algal species (Chlorella, Senedesmus, and Stegioclonium) cultivated in raceway ponds. The oil was extracted by sulfuric acid-catalyzed hot water treatment (150C) from wet microalgae with 80% water content. The extracted microalgal oil was converted to biodiesel using sulfuric acid and methanol by transesterification. To remove the impurities of microalgal biodiesel, biodiesel was finally distillated. The fatty acid methyl ester content of microalgal biodiesel was analyzed.