Proposal for a Conceptual Biorefinery for the Conversion of Waste into Biocrude, H2 and Electricity Based on Hydrothermal Co-Liquefaction and Bioelectrochemical Systems

Microalgal biomass contributes to the valorization of urban and agro-industrial solid waste via hydrothermal co-liquefaction (co-HTL) for the production of biocrude, a sustainable substitute for petroleum. Tropical and populous countries like Brazil generate a lot of agro-industrial waste, such as sugarcane bagasse and malt bagasse, as well as sludge from sewage treatment plants. Such residues are potential sources of biocrude production via thermochemical conversion. To increase biocrude productivity, microalgal biomass has been successfully used in mixing the co-HTL process feed with different residues. In addition to biocrude, co-HTL generates an aqueous phase that can be used to produce H2 and/or electricity via microbial energy cells. In this sense, this paper aims to present the potential for generating energy from solid waste commonly generated in emerging countries such as Brazil based on a simplified scheme of a conceptual biorefinery employing algal biomass co-HTL together with sugarcane bagasse, malt bagasse, and sludge. The biorefinery model could be integrated into an ethanol production plant, a brewery, or a sewage treatment plant, aiming at the production of biocrude and H2 and/or electricity by bioelectrochemical systems, such as microbial electrolysis cells and microbial fuel cells.