Frontier in dark fermentative biohydrogen production from lignocellulosic biomass: Challenges and future prospects

The world's energy consumption is continuously increasing in developing and industrialized nations. However, the rapid depletion of fossil fuels and climate change issues has directed global researchers to think about alternative clean and cost-effective fuels using sustainable approaches to meet the world's energy demand. Biohydrogen production from lignocellulosic biomass (LCB) via dark fermentation is a valuable green fuel to address waste management problems and clean energy production. Further, hydrogen has advantages over other fossil fuels, including high calorific value, high energy efficiency, easy production, and environment friendly alternatives. Additionally, the gaseous emissions and global warming caused by biomass incineration can be decreased by utilizing biomass to produce biohydrogen. Although dark fermentation produces the most efficient and clean biohydrogen, the process's yield and production rate are very low. However, emerging technologies are being researched to increase efficiency and competitive biohydrogen production, especially with dark fermentation. Therefore, the current review emphasises recent developments in the dark fermentative process to enhance the biohydrogen yield and productivity, including various biomass pretreatment technologies, factors affecting the process efficiency, nanoparticles inclusion, bioaugmentation, metabolic engineering techniques, and techno-economic analysis of the biohydrogen generation from LCB. Further, challenges associated with the biohydrogen technology transfer from the lab scale to the industrial scale are examined and highlighted in the future direction of research. Biohydrogen can emerge as a future fuel provided there are low-cost hydrogen production technologies for large-scale efficient production, and policy implementation.