Thermophilic anaerobic co-digestion on coffee ground and food biomass

In Japan, ≈ 10,000 ton/yr of coffee grounds are produced and used as a fuel for boilers or soil conditioner because coffee grounds contain sufficient organic matter. Treating coffee grounds under the co-digestion of foods produced from coffee manufacturing process and waste activated sludge from wastewater treatment process was demonstrated. The potential of the feedstock to produce biogas was studied using AnMBR. About 71.3% COD decomposition rate of blended mixture was obtained, assuming that co-digestion of the present materials is possible. In the continuous experiment, trend of the typical operation parameters, biogas production, pH, VFA, and alkalinity indicated that co-digestion was stable. COD decomposition rate decreased from 67 to 48% corresponding to increasing COD loading rate from 4 to 14 kg-COD/cu m-day. This is an abstract of a paper presented at the International Gas Union Research Conference (Copenhagen, Denmark 9/17-19/2014).