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

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/L R /d) and 90% higher methane yield (448.3 ± 212.9 L CH 4 /kg VS add ) compared to the single-stage. The production of 1.84 m 3 H 2 /m 3 EoL-DPs added in the fermentor increases the overall energetic efficiency of the process.