Acceleration of Biohydrogen Production During Dark Fermentation Using Microbial Immobilised Biochar–Alginate Beads

The transition to renewable energy requires scalable and sustainable hydrogen production technologies. Dark fermentation (DF) can generate biohydrogen from diverse biomass feedstock, but its efficiency remains limited. Immobilising anaerobic consortia offers a route to improve performance. This study reports on the immobilisation of whole cells in hybrid biochar–alginate beads (BAB) compared with control alginate beads (CAB) during DF. Biochar from oakwood and water hyacinth, pyrolysed at 450 and 600/650 °C, were incorporated into BAB. BAB increased biohydrogen production rates by 1.4–2.6-fold relative to CAB, driven by enhanced microbial attachment, synergistic interactions, and improved mass transfer. High-temperature biochar generated the strongest effects, raising hydrogen yield by up to 23% and shortening the lag phase by 94%. Biochar properties, including porosity, surface area, inorganic content, electrical conductivity and buffering capacity, likely support these effects. These results establish hybrid biochar-alginate support as a promising platform to accelerate DF and advance biohydrogen as a sustainable biofuel.