Thermochemical liquidization and anaerobic treatment of kitchen garbage

The pretreatment effect of thermochemical liquidization for anaerobic digestion of kitchen garbage was studied. Model kitchen garbage (dry matter: 11.3%) was thermochemically liquidized at 175 degrees C and 4 MPa with 1 h of holding time. The liquidized garbage was separated into a solid fraction (12.2 wt%) and filtrate (82.9 wt%). The filtrate was anaerobically digested at added volatile solid (VS) concentrations of 1.8-1.9 g/l in a batch system. The biogas yield from the filtrate after 4 d of digestion was 311 ml/g-added VS and the digestion ratio was 67%. The anaerobic treatment of the filtrate indicated fast digestion compared with mechanically disrupted garbage. The diluted supernatant was continuously anaerobically digested by the upflow anaerobic sludge blanket (UASB) method. The range of digestion ratios was 74-75% at an added TOC concentration of 17.0 g/l and an added TOC amount of 1.8-2.8 mg/cm(3)-granule.d. The solid fraction was suggested to be easily processed to refuse derived fuel, based on its low moisture content. The energy balance of the liquidization and anaerobic digestion treatment process was initially analyzed to be better than direct incineration.