Evaluation of recent advances in butanol fermentation, upstream, and downstream processing

Four different processes for butanol production from corn, namely, batch fermentation and distillative recovery (BFDR), batch fermentation and pervaporative recovery (BFPR), fed-batch fermentation and pervaporative recovery (FBFPR), and immobilized cell continuous fermentation and pervaporative recovery (ICCFPR) were evaluated. Pervaporative recovery significantly reduces the cost of butanol production. Depending upon the byproduct credit, which is approximately 3.7 times that of the amount of butanol produced, BFDR, BFPR, FBFPR, and ICCFPR result in a butanol price of $0.55, $0.14-0.39, $0.12-0.37, and $0.11-0.3×kg^-1, respectively. The price of butanol was recently reported at $1.21×kg^-1 by Chemical Marketing Reporter. It should be noted that all three components (acetone, butanol, and ethanol: ABE) diffuse through the pervaporation membrane. Further separation and purification of the solvents would require distillation, which has been considered in this exercise. This article also details the impact of byproduct credit, rate of return, and tax on butanol price.