Waste crude glycerol from biodiesel production can be used to produce biobutanol using Clostridium pasteurianum with the main products being n-butanol, 1,3-propanediol (PDO) and ethanol. There has been much discrepancy and mystery around the cause and effect of process parameters on the product distribution, thus a better understanding of the pathway regulation is required. This study shows that as process pH decreased, the rate of cell growth and CO2 production also decreased, resulting in slower fermentations, increased duration of butanol production and higher butanol concentrations and yields. The production rate of PDO was multi-modal and the role of PDO appears to function in redox homeostasis. The results also showed that C. pasteurianum displayed little biphasic behavior when compared to Clostridia spp. typically used in ABE fermentation due to the alternative glycolysis-independent reductive pathway of PDO production, rendering it suitable for a continuous fermentation process. (C) 2016 Elsevier Ltd. All rights reserved.