Enhancement of dark fermentative hydrogen production using metal-modified biochar from sugarcane residues: Optimization, characterization, and metabolic analysis

This study investigated the enhancement of dark fermentative hydrogen production (HP) using metal-modified biochars derived from sugarcane bagasse (SB) and sugarcane leaves (SL). The biochars were modified with Fe and Ni, with optimal conditions identified through Box-Behnken Design as 6.09 g/L biochar: SB, 5.38 g/L biochar: SL + Fe, and 7.66 g/L biochar: SL + Ni. This optimization achieved a maximum hydrogen yield of 108.77 mL-hydrogen (H₂)/g-glucose, a 58.77 % increase over the control. Metal modification enhanced biochar surface properties and selectively enriched H₂-producing bacteria, particularly Clostridium sensu stricto 1 and Paraclostridium sp. Metabolic pathway analysis showed enhanced glucose catabolism and increased H₂-producing enzyme abundance. The study demonstrates that sugarcane-derived biochar can effectively enhance bio-HP, though careful optimization of metal concentrations is crucial to avoid inhibitory effects.