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.