Biohydrogen production through dark fermentation: Recent trends and advances in transition to a circular bioeconomy

Fossil fuel reserves have drastically decreased over the past two decades, contributing to a worldwide decline in energy sources. The volatility of energy prices and their serious ecological consequences have drawn the attention of researchers to alternative carbon neutral renewable energy sources. Furthermore, ineffective waste management contributes to environmental contamination, harms human health, and negatively affects the global economy. Biohydrogen (Bio-H2) derived from waste biomass via dark fermentation is a valuable green fuel to solve the issues of clean energy production and waste management. Bio-H2 has several advantages over other biofuels, including carbon-neutral production, ease of generation, low carbon dioxide (CO2) emissions, and high energy efficiency. Besides, by using biowaste to produce bio-H2, global warming and CO2 emissions associated with biowaste incineration can be reduced. Although dark fermentation produces the most efficient and clean bio-H2, the yield and rate of production of the process are very low. This review article summarizes the recent developments in dark fermentation processes to enhance bio-H2 yield and productivity, including pre-treatment, additives inclusion, and integrated solutions. Additionally, this article highlights the metabolic pathways of Bio-H2 production and inhibitory substances that negatively affect dark fermentation. Challenges related to bio-H2 technology transfer from lab to industry are discussed, and prospects for future research to realize the technology transfer are briefed. Further, an integrated carbon-neutral approach by dark fermentation-assisted bio-H2 production is also discussed as a contribution to circular bioeconomy. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.