Powdered activated carbon amendment in percolate tank enhances high-solids anaerobic digestion of organic fraction of municipal solid waste

Abstract

Despite many studies recently investigated the addition of conductive materials for enhancing biomethane recovery in anaerobic digestion, there have been limited efforts to adopt this strategy in high-solids anaerobic digestion (HSAD) with percolate recirculation. In this study, two identical lab-scale mesophilic (36 °C) HSAD systems were operated with the organic fraction of municipal solid waste (OFMSW) under similar operating conditions, including food to microorganism ratio and daily percolate recirculation rate. The percolate tank of the test HSAD system was amended with 15 g/L of powdered activated carbon (PAC). After 30 days of operation, the cumulative biomethane yield for the test reactor was 17 % higher than the control reactor (109 vs. 93 L CH4/kg VS). Furthermore, PAC addition showed additional benefits by lowering free ammonia nitrogen (FAN) and volatile fatty acids (VFAs) concentrations that can inhibit anaerobic digestion. Nonetheless, the preliminary economic analysis suggested that the HSAD amended with PAC is practically challenging and will only be economically feasible if PAC can be recycled and reused for the long-term operation or several cycles.