Algal Biodiesel Production Via Extractive-Transesterification using Microwave and Ultrasound Irradiation

This study presents the use of non-conventional methods such as microwaves and ultrasound for algal biodiesel production. Dry algae biomass (Chlorella sp.) was used as feedstock to evaluate three novel single-step extractive-transesterification methods: 1) microwave irradiation with ethanol as solvent/reactant; 2) microwave irradiation with ethanol as reactant and hexane as solvent and 3) ultrasound irradiation with ethanol as solvent/reactant, all catalyzed by sodium hydroxide catalyst. The three novel methods were compared with the conventional Bligh and Dyer method which followed a two-step extraction and transesterification process. The maximum lipid yields for microwave, microwave with hexane, ultrasound, and Bligh and Dyer methods were 20.1%, 20.1% ,18.5, and 13.9%, respectively while the biodiesel (FAEE) conversion of the algal lipids were 96.2%, 94.3%, 95.0%, and 78.1%, respectively. Two comparative process optimization studies (microwave vs. ultrasound and microwave vs. microwave-hexane), algae biomass characterization, FAEE composition analysis and specific energy consumption are presented