Effect of volumetric organic loading rate (OLR) on H2 and CH4 production by two-stage anaerobic co-digestion of food waste and brown water

Two-stage anaerobic digestion system consisting of two continuously stirred tank reactors (CSTRs) operating at mesophillic conditions (37 °C) were studied. The aim of this study is to determine optimum Hydraulic Retention Time (HRT) of the two-stage anaerobic digester system for hydrogen and methane production. This paper also discusses the effect of OLR with change in HRT on the system. Four different HRTs of 48, 24, 12, 8 h were monitored for acidogenic reactor, which provided OLR of 17.7, 34.8, 70.8, 106 g VS/L·d respectively. Two HRTs of 15 days and 20 days were studied with OLR of 1.24 and 1.76 g VS/L·d respectively in methanogenic reactor. Hydrogen production at higher OLR and shorter HRT seemed favorable 106 g VS/L·d (8 h) in acidogenic reactor system. In methanogenic reactor system HRT of 20 day with OLR of 1.24 g VS/L·d was found optimum in terms of methane production and organic removal. The result of this study illustrated the optimum HRT of 8 h and 20 days in acidogenic stage and methanogenic stage for maximum hydrogen and methane production.