Recent Advancements in Microalgal Mediated Valorisation of Wastewater from Hydrothermal Liquefaction of Biomass

Hydrothermal liquefaction (HTL) is an evolving technology that can convert waste with high moisture and low energy content to electricity, heat, hydrogen and other synthetic fuels more efficiently. The lee side is that the HTL process produces enormous amounts of wastewaters (HTWW), having high organic and nutrient load. The discharge of the HTWW would contaminate the environment and result in the loss of valuable bioenergy sources. The valorisation of HTWW has drawn considerable interest. Therefore, this review highlights the valorisation of wastewater during the HTL of biomass. The review paper begins with the discussion of the role of microalgae in valorizing the HTWW. The survey illustrates that the selection of appropriate technology is dependent on biomass characteristics of the microalgae. Finally, potential research opportunities are recommended to improve the viability of the HTL wastewater valorisation for bioenergy production. Overall, this review concludes that combining various processes, such as microalgae-anaerobic digestion, and bio-electrochemical system - microalgae-anaerobic digestion would be beneficial in maximizing HTWW valorisation.