(757d) Simultaneous Biogas Upgrading and Hydrogen Sulfide Removal through Enhanced Electrochemically Assisted Anaerobic Digestion of Food Waste
AIChE Annual Meeting
Friday, November 20, 2020 - 8:30am to 8:45am
To tackle these issues, an innovative system (Fig. 1) incorporating multifunctional bioelectrochemical treatment into the anaerobic digestion of food waste was established for in-situ biogas upgrading and hydrogen sulfide removal. Food waste was hydrolyzed in the upper layer of reactor, and volatile fatty acids were produced and washed down through the percolation layer into the leachate in the lower chamber. A cyclic flow between the lower and upper chambers was created to soak the solids and increase the mass transfer using a peristaltic pump. A pair of electrodes were submersed in the leachate and connected with a direct current power supply. A voltage of 0.3-1.0 V below the requirement of water electrolysis (~1.23 V) was applied. The low carbon steel on the anode was oxidized to release ferrous ions into the leachate, which further combined with aqueous sulfide to generate ferrous sulfide precipitate, thus significantly reducing the gaseous hydrogen sulfide evolution. Meanwhile, on the cathode, some carbon dioxide was reduced to methane through both hydrogenotrophic methanogenesis and homoacetogenesis/acetoclastic methanogenesis pathways. Different combinations of electrode materials (carbon rod, low carbon steel, etc.) and conductive materials (biochar, activated carbon, etc.) were tested to enhance the experimental performances, achieving a high hydrogen sulfide removal efficiency while maintaining minimal material sacrificing rate and electrical charge consumption. Consequently, a hydrogen sulfide removal efficiency over 75% was secured, and the methane content in the biogas was improved to over 80%.