Anaerobic co-digestion of kitchen waste (KW) and wastewater sludge (WS) at different total solids ratios of 1:0, 1:1, 0:1 was conducted under mesophilic temperature conditions (35 ± 1 °C). The co-digestion of kitchen waste and wastewater sludge showed enriched methane gas generation when compared with individual anaerobic digestion of kitchen waste and wastewater sludge individually. The optimum ratio of kitchen waste to wastewater sludge was 1:1. The methane gas yield at 1:1 loading of kitchen waste to wastewater sludge was 43.6%. The total nitrogen content for sludge was 1820 mg/kg. The total nitrogen content of blended was 2180 mg/kg. Cr, Cd, Pb, Mg and Zn were in the kitchen waste and wastewater sludge. © 2016 Informa UK Limited, trading as Taylor & Francis Group.