Eco-efficient butanol separation in the ABE fermentation process

Butanol is considered a superior biofuel, as it is more energy dense and less hygroscopic than the more popular ethanol, resulting in higher possible blending ratios with gasoline. However, the production cost of the acetone-butanol-ethanol (ABE) fermentation process is still high, mainly due to the low butanol titer, yield and productivity in bioprocesses. The conventional recovery by distillation is an energy-intensive process that has largely restricted the economic production of biobutanol. Other methods based on gas stripping, liquid-liquid extraction, adsorption, and membranes are also energy intensive due to the bulk removal of water. This work proposes a new process for the butanol recovery by enhanced distillation (e.g. dividing-wall column technology) using only few operating units in an optimized sequence to reduce overall costs. A plant capacity of 40 ktpy butanol is considered and purities of 99.4 wt% butanol, 99.4 wt% acetone and 91.4 wt% ethanol. The complete downstream processing was rigorously simulated and optimized using Aspen Plus. The enhanced process is effective in terms of eco-efficiency (1.24 kWh/kg butanol, significant lower costs and emissions) and can be readily employed at large scale to improve the economics of biobutanol production.