Osmotic shock pre-treatment of Chaetoceros muelleri wet biomass enhanced solvent-free lipid extraction and biogas production

Abstract

An integrated system for biodiesel and biogas production for the diatom Chaetoceros muelleri was evaluated. We assessed the suitability of osmotic shock pre-treatment of wet microalgal biomass for lipid extraction and biogas production. Osmotic shock pre-treatment released up to 72% of C. muelleri lipid content. Biogas production of pre-treated and lipid-spent microalgae was evaluated by biomethane potential tests and by operating two continuous anaerobic reactors for 200 days. An improvement of 35% in methane production was observed with the pre-treated microalgae in batch conditions, with a maximum methane yield of 521 mL CH4 g VS−1. The methane yield in the continuous experiments of the pre-treated microalgae fluctuated between 0.3 and 0.7 L CH4 g VS−1, with an average of 0.52 L CH4 g VS−1. No significant differences were observed between the pre-treated microalgae without lipid extraction and lipid-spent microalgae in both batch and continuous conditions. The energy potential for a combined biodiesel-biogas biorefinery has been estimated at 20.5 KJ gVS−1 of harvested microalgae.