Coupling a biochar filter to a leach bed reactor for anaerobic digestion of chicken litter

Abstract

In this study, coupling a biochar-packed anaerobic filter (AF) to a batch leach bed reactor (LBR) is investigated as a pragmatic method for biochar application to enhance high-solids anaerobic digestion of chicken litter. Recirculating leachate through a biochar filter reduced solid retention time by 45 % compared with a batch system without recirculation. The key benefit of biochar over inert filter media was the capability to reduce hydrogen sulfide production by 37 % overall; 25 % in the LBR, and 93 % in the AF. No significant differences in methane yield were observed. Biogas produced in the biochar AF was of higher quality with a maximum hydrogen sulfide content of 188 ppm and peak methane content of 73 %. However, majority of the biogas was produced in the LBR due to poor phase separation. Further research is required to increase biogas production in the AF and/or reduce hydrogen sulfide production in the LBR.