A comparative evaluation of dark fermentative bioreactor configurations for enhanced hydrogen production.

Energy from renewable resources has been growing in popularity, which ultimately helps reduce emissions of greenhouse gases (GHGs) and contaminants. Since hydrogen (H) has a higher combustion production of energy than hydrocarbon fuels, it has been identified as a clean, sustainable, and environmentally friendly energy source. There are several benefits to producing biohydrogen (bioH) from renewable sources, including lower cost and increased sustainability. Among the bioH production processes, dark fermentation supports commercialization and scale-up for industrial applications. This paper considers the various bioreactors, such as anaerobic sequencing batch, continuous stirred, up-flow, fixed-bed, and membrane reactors, and their operational approaches for bioH production. This review paper also performs the bibliometric analysis method to identify historical and current developments in a particular field of reactor configuration studies. Furthermore, the main variables influencing reactor performance and methods for increasing process efficiency considering economic and environmental aspects are addressed. The results revealed that continuously stirred reactors are widely utilized for bioH production as a cost-effective reactor configuration. Moreover, the membrane bioreactors and fixed-bed reactors are yielded higher bioH performance than other configurations. Nevertheless, high energy consumption and costs have presented the need for further development of reactors. Consequently, future recommendations to solve the critical problems faced in reactor configurations, the gaps in the literature, and the points that need improvement were comprehensively reported.