Fe2O3 nanocatalyst aided transesterification for biodiesel production from lipid-intact wet microalgal biomass: A biorefinery approach

Abstract Biodiesel production from non-edible feedstock such as microalgae is gaining importance in present day, as they do not interfere with global food economy in addition to higher photosynthetic efficiency as compared to plants. Fresh water grown Neochloris oleoabundans UTEX 1185 is considered as a potential source for biodiesel production. The present study investigated different direct lipid extraction process from wet microalgal biomass through autoclaving, microwave, and ultrasonication pretreatments. Autoclave treatment showed a higher efficiency for lipid extraction as compared to other two pretreatments. Furthermore, transesterification process was carried out in presence of Fe2O3 catalyst and compared with conventional acid (HCl) and base (NaOH) catalysts. Fe2O3 nanoparticles used were synthesized from extract of Hibiscus rosa-sinensis by green procedure. The synthesized Fe2O3 catalyst played an important role in improving the biodiesel yield up to 81%, which is higher than that obtained with HCl (64%) and NaOH (48%). Thereafter transesterification process parameter like catalyst content, reaction temperature and reaction time were optimized and finally 86% biodiesel yield was obtained. Fatty acid methyl esters (FAME) profile analysis and fuel properties revealed the suitability of algal lipid for biodiesel production. 20.2% w/w of carbohydrate present in lipid extracted microalgal biomass was further converted into biohydrogen by dark fermentation and bioethanol under anaerobic condition using acidogenic mixed consortia and Saccharomyces cerevisiae (INVSC-1), respectively. The life cycle assessment study of the overall process was also done.