Novel dual extraction process for acetone–butanol–ethanol fermentation

• A new process concept for butanol removal from fermentation broth was developed.
• Two-stage extraction allows the usage of very effective, non-biocompatible solvents.
• With this new method, very low operational energy consumption can be achieved.
• Optimal solvents are alcohols of 9–12 carbons long with alkanes of the same size.

One reason why butanol fermentation is not economically feasible has to do with the energy intensity of the product separation from the broth. In this study, a new approach for liquid–liquid extraction is presented. Several solvents, previously ignored because of their non-biocompatibility, were tested and a continuous process utilizing a novel, dual extraction with solvent regeneration is proposed. The optimal solvents for this process are from nine to eleven carbon alcohols used in conjunction with alkanes of approximately the same size. The ability to use non-biocompatible, but quite effective solvents offers a significant advantage, which is why a very low energy consumption of 3.76 MJ kg−1 butanol is achieved with this new process.