The anaerobic treatability and methane generation potential of three different cotton wastes namely, cotton stalks, cotton seed hull and cotton oil cake were determined in batch reactors. In addition, the effects of nutrient and trace metal supplementation were also investigated. To this purpose biochemical methane potential (BMP) experiments were performed for two different waste concentrations, namely 30 and 60g/l. The results revealed that cotton wastes can be treated anacrobically and are a good source of biogas. Approximately 65, 86 and 78 ml CH4 were produced in 23 days from 1 g of cotton stalks, cotton seed hull and cotton oil cake in the presence of basal medium (BM), respectively. BM supplementation had an important positive affect on the production of biogas. (c) 2006 Elsevier Ltd. All rights reserved.