Synergistic enhancement of biohydrogen production from grass fermentation using biochar combined with zero-valent iron nanoparticles

In this paper, the improving roles and mechanisms of grass hydrogen fermentation by biochar combined with zero-valent iron nanoparticles (Fe0 NPs) were investigated. The experimental results revealed that biochar (600 mg/L) combined with Fe0 NPs (400 mg/L) synergistically enhanced microbial activity and enriched much more Clostridium species, which contributed to more efficient metabolic pathways for synergistically improving hydrogen productivity and substrate utilization. It is proposed that the synergistic effect was attributed to the complementary functions of biochar and Fe0 NPs in the system and the release of more Fe2+ from the Fe0 NPs-biochar micro-electrolysis. Hydrogen yield reached 50.6 mL/g-dry grass when biochar + Fe0 NPs were added, which was 89.8%, 53.3% and 15.9% more than that for the control group, the individual biochar and individual Fe0 NPs group, respectively. The addition of biochar + Fe0 NPs also shortened the lag phase and enhanced the hydrolysis of grass, which accelerated the hydrogen fermentation process. This investigation demonstrated that biochar combined with Fe0 NPs is an effective method for improving the process efficiency of biohydrogen production from grass fermentation.