Co-Digestion of Dehydrated Sewage Sludge (DSS) and Organic Fraction of Municipal Solid Waste (OFMSW): Analysis of the Process and Economic Evaluations

Abstract

This study aimed to assess the efficacy of anaerobic digestion (AD) in the co-digestion of the organic fraction of municipal solid waste (OFMSW) and municipal dehydrated sewage sludge (DSS). The experiments were conducted in batch and continuous mode under mesophilic conditions (T = 37 ± 2 °C). The results of batch tests indicated that the use of DSS in co-digestion with OFMSW led to a biomethane production of 422 NmLCH4/gVS with a production yield of 450 NmLCH4/gVSremoved. Nevertheless, the findings of the tests conducted with OFMSW alone demonstrated superior performance. A pilot plant reactor with a volume of approximately 2 m3 was employed in the continuous tests. The results corroborated the trends observed in the batch tests. In particular, the specific methane production yields decreased from 0.47 Nm3/kgVS when OFMSW was the sole substrate to 0.44 Nm3/kgVS when DSS was introduced, with a DSS/OFMSW ratio (RDO) of 0.1. Despite the reduction in methane production yield observed in both batch and continuous tests, a techno-economic assessment of the process indicated the potential profitability of DSS in co-digestion with OFMSW. Notably, the estimated profit from utilizing DSS in a percentage of 10% (RDO = 0.1) is 108 EUR/ton, compared to 102 EUR/ton when only OFMSW is employed.