The production of butanol from thin stillage by Clostridium pasteurianum DSM 525 was evaluated in the paper. At initial pH values ranging from 5.0 to 7.0 C pasteurianum DSM 525 produced 6.2-7.2 g/L of butanol utilizing glycerol in thin stillage as the main carbon source, with yields of 0.32-0.44 g butanol produced/g glycerol consumed, which are higher than previously reported yields (e.g., 0.14-0.31 g butanol/g glycerol, Biebl, 2001). Lactic acid in the thin stillage acted as a buffering agent, maintaining the pH of the medium within a range of 5.7-6.1. Lactic acid was also utilized along with glycerol, enhancing butanol production (6.5 g/L butanol vs. 8.7 g/L butanol with 0 and 16 g/L lactic acid, respectively). These results demonstrate the feasibility of cost-effective butanol production using thin stillage as a nutrient-containing medium with a pH buffering capacity. (C) 2011 Elsevier Ltd. All rights reserved.