Critical Analysis of Various Strategies for the Effective and Economical Separation and Purification of Butanol from ABE Fermentation

ABSTRACT Biobutanol is a potential biofuel produced from various biomass and can serve as a suitable alternative to the nonrenewable fossil-based gasoline fuel. The fermentative microbes used for biobutanol production are solvent-producing Clostridium organisms by Acetone-Butanol-Ethanol (ABE) fermentation. The major challenges of ABE fermentation are butanol toxicity to the host strain, lack of effective fermentation strategies, inefficient butanol separation, and low 0.5–2% w/w yield. Butanol forms an azeotropic mixture with water and requires 79.5 MJ/kg energy for separation using conventional distillation when the energy content of butanol is only 36 MJ/kg; hence the separation by traditional distillation processes is inefficient. Recent developments in membrane technology, coupled with novel extractants and adsorbents, are promising for efficient, energy-effective, and economical bio-butanol separation. Among the techniques, liquid-liquid extraction has shown a high separation efficiency of 75–85% butanol with an energy demand of 25 MJ/kg, whereas adsorption and pervaporation have shown an energy demand of 35–40 MJ/kg. In the present review, a critical analysis of the recent trends, strategies, technical prospects, challenges, and economical evaluation of different methods of biobutanol recovery is presented.