Algal biomass dual roles in phycoremediation of wastewater and production of bioenergy and value-added products

Abstract

Algal biomass has been gaining attention over the last decades as it is versatile and can be used in different industries, such as wastewater treatment and bioenergy industries. Microalgae are mixotrophic microorganisms that have potential to utilize nitrogen and phosphate (nutrients) and remove organic matters from wastewater streams. Phycoremediation is an intriguing and cost-efficient technique to simultaneously remove heavy metals from wastewater while removing nutrients and organic matters. The cultivated and produced algal biomass can be a promising candidate and a sustainable feedstock to produce biofuels (e.g., biodiesel, bio-alcohol, and bio-oil) and value-added products such as biochar, glycerol, functional food, and pigments. The algae suspended cultivation systems, WSP and HRAP, are efficient methods for the wastewater treatment in shallow ponds with no mechanical aeration and less required energy consumption, but when a short HRT and minimum evaporation losses are key points in the algal cultivation the PBRs are recommended. It was reported that biosorption and bioaccumulation are the two promising techniques of phycoremediation. Studies showed that among the current processes of algal biomass conversion to biofuels, transesterification of algal lipids and pyrolysis of algal biomass were found to be the most efficient techniques. This review paper investigates the applications of algal biomass in the phycoremediation of wastewater, productions of bioenergy and value-added products by reviewing articles mainly published over the last five years.Graphical abstract