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

• Unmodified biochar added to a digester resulted in 90.5% H 2 S removal efficiency. • The biochar particle size did not significantly affect the H 2 S removal efficiency. • Iron-impregnated biochar resulted in complete removal of H 2 S from the biogas. • Activated carbon was not effective when used as an in-situ desulfurization agent. • Biochar addition did not significantly affect the methane yield during digestion. Corn stover biochar (CSB) and maple biochar (MB) were added into anaerobic digesters and evaluated for hydrogen sulfide (H 2 S) reductions. This was the first study to show Fe-impregnated biochar can eliminate H 2 S production. The novel study evaluated biochar addition on H 2 S 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), H 2 S production was 90.5% less than the control treatment (351 mL H 2 S/kg VS). Biochar particle size did not significantly affect H 2 S concentration. The Fe-impregnated biochar (0.5 g biochar/g manure TS) reactors had no H 2 S detected in the CSB-Fe system. Methane (CH 4) 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 H 2 S production without affecting CH 4 production. [ABSTRACT FROM AUTHOR]