The Contribution of Microalgae in Bio-refinery and Resource Recovery: A Sustainable Approach leading to Circular Bioeconomy

Abstract

Population growth supplemented by urbanization and industrial developments has led to elevate the global energy demands, building up risk for the finite and non-renewable petroleum reserves. Besides being at the verge of getting exhausted fossil fuels are major contributors of greenhouse gases to the environment. This led to the expedition for sustainable and renewable energy source and researchers found microalgae an over overwhelmingly rich source of renewable energy, which are termed as tiny biorefineries. Microalgae are the eukaryotic /prokaryotic organisms having the capabilities of fixing carbon (1 kg of algal biomass can fix about 1.5 kg of CO2) photosynthetically (8.3 % photosynthetic efficiency). The diversified nature of different genera of microalgae allows them to be grown in varying cultivating conditions i.e., high ammonia acidic/basic pH, varied salinity, high/low temperatures. Microalgae are regarded as third generation feedstock in the production of algal biomass which is a source of biofuels and other value-added products. The cost effectiveness is the criterion where microalgae-based biofuels lose the ground to fossil fuels since the cost of cultivation and harvesting is high. But the cost issue can be suppressed if microalgae is cultivated coupled with wastewater resulting in the resource recovery and biomass production at the same time. This can be achieved by blending biorefinery with bioeconomy. Biorefinery paves the way to obtain biofuels and other green chemicals from microalgal biomass and circular bioeconomy directs the best optimum utilization of the obtained microalgal biomass for sustainable and environmentally friendly system. As it promotes the primary objectives of the circular bioeconomy (i.e., reduce and reuse). Valorization of a single product from microalgal biomass is not valued, as it restrains the economic viability, while multiple products from microalgal biomass which are commercially in demand and are environmentally sustainable can compensate the economy. Consolidating bioeconomy in microalgal biorefinery can improve cost-effectiveness and process efficiency, together with resource recovery. This mini review focusses on the primary components of the circular bioeconomy in context of the high pollutants/nutrient composition of different wastewaters. This review gives the overview for the circular bioeconomy concept in biorefinery approach to produce biofuels from microalgae and other useful products, simultaneously treating wastewaters.