In this project, thermophilic anaerobic digestion of the kitchen waste was investigated. With the majority of the source separated kitchen waste is used in the feedstock of pig production and in composting, this project aims to provide an engineered option for kitchen waste recycling. The pilot plant is located in the farm in Tainan county. Dimension of the reactor is 4.55 m (L) x 1.80 m (W) x 1.80 m (H), and was separated into two compartments: the acidogenesis chamber (volume = 1.2 m3) and the methanogenesis (volume = 12.4 m3). Thermophilic condition of the reactor was maintained through the heaters installed in both chambers at about 55oC. In addition to the temperature and pH sensors, ORP sensor was also installed in the methanogenesis chamber. System was started with the seeding of the anaerobic sludge from a nearby pig farm. When the system became stable, influent of the kitchen waste was from 100 L/d and gradually increased to 500 L/d (with 5 days per week). Volumetric loading rates (VLR) of the system were between 1.1-4.3 kg TCOD/m3-d, and the hydraulic retention times (HRT) of the reactor was decreased from 68 days down to 27 days. Removal efficiencies of TCOD, SS, and VSS were between 76.8-92.5%, 64.3-79.6%, and 73.1-85.4%, respectively. Under the flowrate of 500 L/d, gas production was found to be around 4000 L/d, with the methane content between 52-66%. Sodium concentration in the reactor was found to be less than 1000 mg/L, but the O&G in the influent was found to be around 25000 mg/L, after the acidogenesis about 8000-14000 mg/L remained, and even in the methanogenesis stage about 3000-4000 mg/L of O&G was observed. When the O&G levels are higher than 20000 mg/L, retardation and possible inhibition might occur. It is suggested that the EPA should set up some demonstration plants to encourage local governments to adopt the TAnD approach as an option for kitchen waste recycling and reuse.

Kitchen Waste,Thermophilic Anaerobic Digestion,Resource Recovery