This paper discusses the methanogenic digestion of a synthetic acetic acid wastewater inoculated using a mixed culture obtained from an anaerobic digester at a municipal wastewater treatment facility. Experiments were conducted in 500 mL batch reactors containing an unbuffered acetic acid solution. Test conditions compared methane production and acetic acid degradation at both acidic (pH 4.5) and neutral (pH 7.0) initial system conditions. Results showed that methane production increased by 30% when the initial pH was decreased from 7.0 to 4.5. (c) 2006 Elsevier Ltd. All rights reserved.