Biochar addition with Fe impregnation to reduce H2S production from anaerobic digestion

Corn stover biochar (CSB) and maple biochar (MB) were added into anaerobic digesters and evaluated for hydrogen sulfide (H2S) reductions. This was the first study to show Fe-impregnated biochar can eliminate H2S production. The novel study evaluated biochar addition on H2S reduction and nutrient concentrations using three experiments to test the effect of: 1) biochar concentration, 2) biochar particle size, and 3) Fe-impregnated biochar using triplicate lab-scale reactors. At the highest biochar dose (1.82 g biochar/g manure TS), H2S production was 90.5% less than the control treatment (351 mL H2S/kg VS). Biochar particle size did not significantly affect H2S concentration. The Fe-impregnated biochar (0.5 g biochar/g manure TS) reactors had no H2S detected in the CSB-Fe system. Methane (CH4) in the biochar and control treatments were not significantly different in all three experiments. The results show that biochar added to digesters can significantly reduce H2S production without affecting CH4 production.