Anaerobic co-digestion of End-of-Life dairy products with agroindustrial wastes in a mesophilic pilot-scale two-stage system: Assessment of system’s performance

[Display omitted] •EoL-DPs can be efficiently co-digested with AgW at ∼20% (w/w) of overall feedstock.•Pilot-scale co-digestion of EoL-DPs with AgW was demonstrated in a two-stage system.•Acidification of EoL-DPs alone should precede their co-digestion with AgW.•Two-stage co-digestion produces 50% more methane (0.51 L/LR/d) than single-stage.•1.84 m3 H2 gas and 29.53 m3 CH4 may be produced per m3 EoL-DPs. This study aimed to demonstrate the co-digestion of End-of-Life Dairy Products (EoL-DPs) with a typical mixture of Agroindustrial Wastes (AgW) in a pilot-scale two-stage mesophilic (37 °C) anaerobic system and compare its performance under single-stage operating conditions. The system was initially operated in the two-stage mode, with the fermentor fed exclusively with EoL-DPs which, after acidification, were co-digested with AgW in the methanogenic bioreactor. In the second operating scenario, the raw EoL-DPs and AgW were directly fed and co-digested in the digester. Both systems were operated at Hydraulic Retention Time of 37 days with the EoL-DPs mixture accounting for ∼20% (w/w) of the total feeding stream. At the two-stage mode, the digester exhibited 50% higher methane productivity (0.51 ± 0.27 L/LR/d) and 90% higher methane yield (448.3 ± 212.9 L CH4/kg VSadd) compared to the single-stage. The production of 1.84 m3 H2/m3 EoL-DPs added in the fermentor increases the overall energetic efficiency of the process.