A comprehensive insight from microalgae production process to characterization of biofuel for the sustainable energy

•A detailed review on various microalgae harvesting methods was carried out.•Discussed the various types of oil extraction and biodiesel production.•Elaborate studies on various algae were presented.•Various applications of algae was discussed.•Downstream and upstream process of algae biofuel were discussed. The present article reviews about the algae isolation, microalgae growth, types of cultivation, oil extraction, biodiesel characterization and the advantage of microalgae biomass and its other applications. A detailed review was undertaken on various microalgae harvesting methods, types of oil extraction and biodiesel production. The merits and demerits of open pond systems and photo-bioreactors cultivation are discussed briefly. The various microalgae species and its lipids used for biodiesel production were presented and compared with conventional feedstocks. This article also discusses the key process parameter for in-situ transesterification for biodiesel production such as molar ratio, stirring rate, moisture, reaction time, catalyst type and temperature. The fundamental characterization of the biodiesel and physiochemical properties such as flash point, cetane number, density, kinematic viscosity, pour and cloud point and calorific value were studied and compared with the results of conventional diesel. This study reports that oil from microalgae can be a suitable alternative than edible oils due to ease of growth, separation, and high lipid content. The properties of microalgae biodiesel meet ASTM standards. Overall, algae are not only a potential source for biofuel but can also be used in wastewater treatment, food additives, carbon sequestration, heath care, cancer treatment and aquaculture all of which are discussed in this review.