Use of Ultrasound and Co-Solvents to Improve the In-Situ Transesterification of Microalgae Biomass

The conversion of microalgae lipids to biodiesel has been increasingly investigated, with the use of the in-situ transesterification method reported in the literature to lead to improved alkyl ester conversions for this feedstock compared with the use of the conventional two staged oil extraction and transesterification process. To further improve the feasibility of the use of the in-situ method, this paper investigates modifications to reduce the large process methanol requirements, and potentially improve the oil to methyl esters conversion and biodiesel yields. The results obtained showed that use of ultrasound agitation for the in-situ process, as well as combining this stirring regime with co-solvent use (n-pentane and diethyl ether) significantly improved the Chlorella oil to methyl esters conversion with reduced reacting methanol volumes.