Abstract: This paper investigates the anaerobic biodegradability of blackwater and its suitability for co-digestion in batch digesters (eudiometers) under mesophilic temperature. Readily available co-substrates such as grease trap waste, concentrated urine and high strength domestic wastewater which are high-strength organic substrates were introduced. These substrates were treated in a decentralized reactor through anaerobic digestion. The biomethane potential of these substrates at different inoculum to substrate ratios was investigated using 250 mL reactor bottles according to DIN 38414-8. Biogas production and quality was measured on a regular basis to determine the extent of the substrate degradation in terms of biogas production, volatile solids and chemical oxygen demand reductions, methane content and methanation level. The co-digestion experiments revealed that blackwater is best co-digested with grease trap waste based on the increased biogas production of 57 percent and the enhanced biogas quality. The co-digestion of blackwater with urine is only possible up to 10 percent v/v addition due to inhibition by ammonia at higher urine fractions.