Continuous anaerobic digestion of food waste and design of digester with lipid removal

Abstract

Separation of municipal solid waste has been implemented in many cities in China. As a major component of municipal solid waste, food waste can be treated by anaerobic digestion (AD) for energy production. To provide reference data for disposing of food waste through engineering applications, continuous AD was carried out under various organic loading rates (OLRs) at 27±2°C in the laboratory. The anaerobic reactor was stable with pH 7.0–7.1, total volatile fatty acid (VFA) concentrations of 206–746 mg/L, and concentrations of 525–1293 mg/L when the OLR was 1.118–5.588 kg volatile solids (VS)/m3·d. The maximum volumetric biogas production rate was 4.41 L/L·d when the OLR was increased to 5.588 kg VS/m3·d with a hydraulic retention time of 30 d. When the OLR was increased to 6.706 and 8.382 kg VS/m3·d, biogas production was seriously inhibited by VFAs, with maximum total VFA and propionate concentrations of 8738 mg/L and 2864 mg/L, respectively. Due to the incomplete degradation of lipids, the specific methane production rate of 353–488 L/kg VS accounted for 55.2–76.3% of the theoretical methane potential calculated based on the component composition. A retrofitted anaerobic digester with lipid removal was designed to improve the efficiency.