BACKGROUND: Municipal bio-wastes (MBW) yield soluble bio-based substances (SBO) by anaerobic digestion, composting and chemical hydrolysis. The SBO are known valuable products for multiple uses in the chemical industry, agriculture and animal husbandry. The present work investigates a new SBO property, i.e. reducing the ammonia content in MBW anaerobic digestates. Thus, MBW were fermented under anaerobic conditions with 0.05 or 0.20% SBO added. RESULTS: Fermentations were carried out at 55 degrees C for 14 days using nine batch reactors of 6.5 L capacity working in parallel, each containing 4 L MBW slurry (100 g volatile solids). The control and SBO 0.05% reactors produced 70 L of biogas, and 1.2 g and 0.11 g ammonia N, respectively. The SBO 0.20% reactors produced 73 L biogas and a digestate containing 0.32 g less ammonia N than the starting ammonia content. Oxidation of ammonia to N-2 promoted by SBO seemed the most likely reason for the ammonia reduction. The process benefits were evaluated in comparison with conventional technology for the abatement of ammonia. CONCLUSIONS: Integration of biochemical and chemical technology yielding multipurpose products from MBW is a potentially viable cost-effective feasible route to turn a MBW treatment plant into a biorefinery. (C) 2015 Society of Chemical Industry