The effect of co-digesting slaughterhouse waste (SHW) with waste mixed sludge (WMS) for possible implementation in a full-scale digester in an existing wastewater treatment plant (WWTP) was investigated. Biomethane potential (BMP) runs were activated using SHW:WMS ratios from 0% to 60% at total solids (TS) of 4% and 7%. Higher values of BMP of about 735 NLCH4/kg volatile solids (VS) were obtained for the run with a SHW:WMS ratio of 40% and TS = 4%. Continuous runs were also performed using the same SHW:WMS ratio at different organic loading rates (OLR). The maximum biomethane generation of 550 NLCH4/kgVS was achieved for an OLR = 1.5 kgVS/m(3).day. Stability monitored by FOS/TAC showed values < 0.7 for OLR up to 2.0 kgVS/m(3).day. The amount of SHW processable in the full-scale digester of the WWTP ranged from about 1.8 MgTS/day to 3.0 MgTS/day with a biomethane production of about 2300 Nm(3)/day and 1400 Nm(3)/day, respectively. (C) 2019 Elsevier Ltd. All rights reserved.