Maximum organic loading rate for the single-stage wet anaerobic digestion of food waste

Anaerobic digestion of food waste was conducted at high OLR from 3.7 to 12.9 kg-VS m−3 day−1 for 225 days. Periods without organic loading were arranged between the each loading period. Stable operation at an OLR of 9.2 kg-VS (15.0 kg-COD) m−3 day−1 was achieved with a high VS reduction (91.8%) and high methane yield (455 mL g-VS-1). The cell density increased in the periods without organic loading, and reached to 10.9 × 1010 cells mL−1 on day 187, which was around 15 times higher than that of the seed sludge. There was a significant correlation between OLR and saturated TSS in the sludge (y = 17.3e0.1679×, r2 = 0.996, P < 0.05). A theoretical maximum OLR of 10.5 kg-VS (17.0 kg-COD) m−3 day−1 was obtained for mesophilic single-stage wet anaerobic digestion that is able to maintain a stable operation with high methane yield and VS reduction.