Approach to microalgal biodiesel production: Insight review on recent advancements and future outlook

The environmental concerns about fossil energy and rising oil prices are regular global phenomena. In such an exigency where fossil fuel sources are dwindling, carbon-neutral biodiesel derived from microalgae lipid seems to be an important renewable energy resource. In recent years, microalgae have become a lucrative feedstock for economically viability of commercial-scale biofuel production owing to its high biomass growth and high oil yield compared with other crops. The screening and selection of promising microalgae strain should be based on their fatty acid profile and culture conditions. The laboratory to pilot scale culture of microalgae species requires systematic experimental designs to maximize microalgal growth using open or raceway ponds, closed photo bioreactors and hybrid systems. The pros and cons of each harvesting technique, including filtration, centrifugation, sedimentation and flocculation as well cell disruption by thermal, mechanical, chemical and biological techniques, are deliberated in details. Furthermore, the application of homogeneous, heterogeneous and enzyme catalysts in transesterification processes as well as purification technologies are emphasized to ensure high-quality biodiesel production as per ASTM norms. Microalgae comprise a potential feedstock and biodiesel synthesis from them requires a series of complex up-streaming and down-stream processes which are inherently disadvantageous in technology transfer from laboratory to industrial scale. This review paper is mainly focused on microalgal cultivation, harvesting, oil extraction, biodiesel production and purification technologies, and each vital process is critically reviewed in each step. (c) 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.