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 (Fe-0 NPs) were investigated. The experimental results revealed that biochar (600 mg/L) combined with Fe-0 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 Fe-0 NPs in the system and the release of more Fe2+ from the Fe-0 NPs-biochar micro-electrolysis. Hydrogen yield reached 50.6 mL/g-dry grass when biochar + Fe-0 NPs were added, which was 89.8%, 53.3% and 15.9% more than that for the control group, the individual biochar and individual Fe-0 NPs group, respectively. The addition of biochar + Fe-0 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 Fe-0 NPs is an effective method for improving the process efficiency of biohydrogen production from grass fermentation.