Mineral Requirements for Mesophilic and Thermophilic Anaerobic Digestion of Organic Solid Waste

Anaerobic digestion of organic solid waste (OSW) from kitchen was conducted in completely stirred tank reactors (CSTRs) under both mesophilic and thermophilic conditions. The lab-scale reactors were fed with the OSW containing 10% of total solids (TS) at a hydraulic retention time (HRT) of 30 days (3.0-3.5 g-TS/L/d of volumetric loading rate). Both mesophilic and thermophilic reactors exhibited process failure due to severe acidification. A restoration of methane yield based on the volatile solids (VS) of the OSW added was observed after the addition of minerals (Ni, Co, and Fe) in the mesophilic reactor but not in the thermophilic reactor, suggesting that the requirement for minerals is higher in thermophilic anaerobic digestion than in mesophilic digestion. It is suggested that, among those minerals, Ni is the most important for anaerobic digestion of the OSW.