To summarize, a very stable anaerobic digestion process with specific methane yields of about 300 Nm3 tCOD1 (66–69 vol.% CH4) is possible by adjusting an OLR of 2.5 kgVSm3d1 and ammonia concentration not exceeding 6.0 g/kg. If slight accumulation of VFA (between 2000 and 4000 mg/kg) and slightly lower specific methane yields (260–280 Nm3 tCOD1) are acceptable, still reasonable
performance was still observed at an elevated ammonia concentration above 6.0 up to 7.5 g/kg. If the ammonia concentration exceeds 7.5 g/kg, the overall process performance drops significantly