Creating value from acidogenic biohydrogen fermentation effluents: An innovative approach for a circular bioeconomy that is acquired via a microbial biorefinery-based framework

Abstract

As a response to the environmental and societal issues that emanate from the high reliance on fossil fuels, the world is now transitioning toward a circular bioeconomy. Acidogenic biohydrogen production is envisaged as a clean fuel of the future due to its non-polluting features and affordability. The major encumbrance for the industrialization of this process is due to the accumulation of metabolic inhibitors (volatile fatty acids (VFAs)), which lower the H2 yields. This review discusses novel methods that can be adopted to valorize the acidogenic VFAs via a “cascade microbial biorefinery-based” approach that enables this process to be economically feasible as it leads to the concomitant production of diverse high-value-added products. The work also elucidates the key setpoint parameters governing the recovery of VFAs during the acidogenic H2 process. It further explores the recent advances in the use of VFAs in microbial biorefineries. Finally, the paper provides some recommendations that might help develop acidogenic microbial biorefineries in the future. Studies focusing on microbial biorefineries tailored towards the valorization/beneficiation of acidogenic VFAs are very scarce in the literature. This work aims to provide new insights into microbial biorefinery-based processes involving the use of acidogenic VFAs as substrates.