Butanol can be produced by fermentation from corn, molasses or lignocellulosic biomass for use as a chemical or superior biofuel. However,
butanol's production is hampered by its toxicity to the microbial culture that produces it. In fermentation broths, final butanol concentrations typically range from 13-18 g/L, which is low. Also its boiling point (118 °C) is higher than water (100 °C), which makes its recovery energy intensive. To make it an energy efficient process, alternate recovery techniques such as pervaporation are sought. In search of these membrane processes, we have intensified our research in this direction. We have tested POMS, silicone, polypropylene, and silicalite membranes for butanol separation from model solutions and fermentation broths. Model solutions offer high flux and selectivities, however, use of actual fermentation broth results in reduced selectivity and flux which are membrane specific. Furthermore, lignocellulosic hydrolyzates as feedstocks are turbid and they adversely affect the membrane performance.
Pervaporation will be compared with other process separation options like gas-stripping, liquid-liquid extraction, and adsorption. Including the final
purification step, all mentioned process separation options need a final purification step using distillation. For an energy efficient hybrid separation system it is important that the separation step prior to distillation achieves the highest selectivity possible, which leads to lower energy demand in distillation and the total hybrid separation system. This presentation will cover an overview of recovery of butanol (acetone-butanol-ethanol, ABE) from fermentation broth.