The biorefinery idea has been known because the most promising thanks to produce a biomass-based trade, which might be outlined because the property biomass process to get energy biofuels and high-value product through processes and instrumentation for biomass. Microalgae is used as AN economical and economically viable biorefinery feedstock; microalgae may well be employed in totally different areas like human and animal nutrition, nutraceutical and therapeutic product, fertilizers, plastics, isoprenes and biofuels and conjointly within the treatment of wastewaters and greenhouse gas capture. Microalgae biomass is used for biofuel production, like organic phenomenon, methane, biohydrogen, bioethanol and biodiesel. during this chapter, an outline of the factors that have an effect on the assembly of the microalgal biomass yield and added by-products production is bestowed. A biorefinery will utilize all types of biomass like wood, agricultural crops, organic waste, industrial and domestic wastes and aquatic biomass. The microalgae gift a high potential for the biodiesel production compared to the terrestrial biomass.