MBfR for biomethanation
The hydrogenotrophic conversion of carbon dioxide (CO2) and hydrogen (H2) gases to methane (CH4), frequently defined as biomethanation, presents a viable alternative to fossil-based natural gas. In this study, a membrane biofilm reactor (MBfR) was newly designed to support robust methanogenic biofilm formation and enhance CO2 and H2 conversion under minimal mixing conditions and without nutrients supplementation. Over the 437-day operation, a thick, uniform, proteins-rich biofilm developed on top of the PDMS membrane, and the MBfR sustained methane productivity for 396 days without additional nutrient supply. In both biofilm and mixed liquor microbial community was dominated by the hydrogenotrophic methanogen Methanothermobacter together with a putative new Hydrotermae spp. bacterium,  likely utilizing H2 and CO2 for homoacetogenesis and fermenting detrital biomass. The MBfR design presented in this study offers a promising strategy for scalable, energy-efficient biological methanation optimizing H2 utilization with minimal nutrient input.