The possibility of using tannery raw wastewater as substitute for the nutrient supply in the anaerobic co-digestion of two tannery solid waste was investigated with regard to energy efficiency, waste treatment efficiency and economic efficiency. The results showed that the use of tannery wastewater as a source of nutrients for the AD of solid tannery waste proved to be adequate from the point of view that the three residues are being treated simultaneously. There was a biogas production of only 1.9 +/- 0.3 mL/VSS. However, the percentage of methane in the biogas reached 33 % at the beginning of the process, proving that there was methanogenic activity and that AD established. The cost analysis showed that there is a great reduction in the cost of wastewater treatment and solid waste disposal of 23 % and 18 %, respectively, in terms of electricity consumption and 11 % and 8 % respectively in terms of thermal consumption. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.