Recent advances in wastewater microalgae-based biofuels production : a state-of-the-art review

Rapidly expanding industrialization and the depletion of non-renewable fossil fuels have necessitated the discovery of feasible renewable alternatives to meet the rising energy demand while reducing carbon dioxide (CO2) emissions. The present global energy strategy is built on cost-effective and environmentally friendly alternatives; and production of microalgae has the ability to meet these requirements. Microalgae have been found as a promising and sustainable alternative for treating wastewater (WW) concurrently with biofuel production. One potential strategy, which uses microalgae for lowering the level of contamination in WW is called bioremediation. There are substantial gains to be made for both the economy and the environment through the integration of microalgae-based biofuel production with wastewater treatment (WWT). The use of microalgae that have a short life span, a high growth rate, and a high CO2 usage efficiency is one of the promising approaches for producing biomass from WW nutrients that involves the utilization of renewable resources. Microalgae are one of the most promising biomass resources for use in thermochemical conversion processes for the production of liquid and gaseous biofuels due to their advantages over other biomass feedstocks, such as sustainability, renewability, and productivity. Currently, technology and cost are the primary obstacles limiting industrial applicability, which necessitates an optimum downstream process to minimize production costs. Consequently, the concurrent utilization of microalgae for WWT and biofuel production has made these challenges practical and economically viable. This review provides an overview of microalgae and their bioremediation and bioenergy production applications. It also provides insight for future research to investigate additional possible applications of microalgal biomass. These applications could include not only the bioremediation process, but also the generation of revenues from microalgae through the incorporation of clean and green technology, which would provide long-term sustainability and environmental benefits. (C) 2022 The Author(s). Published by Elsevier Ltd