Biofuels from microalgae biomass: A review of conversion processes and procedures

Abstract

• Key areas for improvement in microalgae conversion include the nature of catalysts been utilized. Bio-based catalysts should be preferred due to high cost of synthetic catalysts. Methodical limitations such as high equipment cost for process scale-up can prevent research from advancing as it could. • Promising microalgae conversion processes which could be progressed are the use of bio-based solvents and supercritical fluids for biodiesel production, hydrothermal liquefaction for biogas production, microwave-induced pyrolysis for syngas production, and ultrasound/microwave enhanced extraction for bio-oil production. • For future developments, the use of the promising conversion techniques would probably gain the interest of more researchers than at present, considering the merits of same. In other words, more research is expected to evolve in coming years. Achieving the EU 2030 vision of a 15% minimum amount of biofuels utilized in the road transportation require more research on biofuel production from biomass feedstock. To this end, this review study examines the use of green, deep eutectic solvents and direct transesterification approaches for biomass conversion to biofuels. Next, biogas production from anaerobic co-digestion of microalgae biomass is presented. Lastly, the effect of operating conditions, as well as advantages and limitations of several biomass conversion techniques are outlined. Of note, this study presents promising microalgae conversion processes which could be progressed are the use of bio-based solvents and supercritical fluids for biodiesel production, hydrothermal liquefaction for biogas production, microwave-induced pyrolysis for syngas production, and ultrasound/microwave enhanced extraction for bio-oil production. These are based on the possibility of high yield and process economics. We have also enumerated knowledge gaps needed to propel future studies.