Anaerobic digestion of food waste through the operation of a mesophilic two-phase pilot scale digester - Assessment of variable loadings on system performance

Single and two-phase operations were compared at mesophilic operating conditions using a digester system consisting of three 5-m3 reactors treating food waste generated daily within the university campus kitchens. When normalizing the methane production to the daily feedstock characteristics, significantly greater methane was produced during two-phase mesophilic digestion compared to the single-stage operation (methane yield of 380 vs 446-L CH4 kg VS−1; 359 vs 481-L CH4 kg COD−1 removed for single vs two stage operation). The fermentation reactor could be maintained reliably even under very low loading rates (0.79 ± 0.16 kg COD m−3 d−1) maintaining a steady state pH of 5.2.