Butanol Recovery from Fermentation Broth Using Reverse Osmosis

This chapter summarizes the current research on the application of reverse osmosis (RO) for the separation of butanol from acetone–butanol–ethanol (ABE) fermentation broth. A brief overview of fermentation process is also included in the chapter. Recovery of butanol from fermentation broths is a critical step in the production process, as it directly impacts the efficiency and economic feasibility of the process. RO is a pressure-driven membrane-based separation technique that emerges as a promising alternative due to its lower energy requirements and favorable recovery of butanol. RO enables selective separation based on molecular size, solubility, and osmotic pressure, offering a more energy-efficient and sustainable option compared to conventional methods. A complex mixture containing ABE and various organic acids elevates osmotic pressure. Butanol concentration in the fermentation broth is generally low, typically ranging from 10 to 26 g/L. Effective butanol recovery via RO process requires careful consideration of several key factors, including membrane material, membrane selection, operating conditions, pressure, permeate flux, concentration polarization, and fouling. The buildup of fermentation byproducts, including proteins and lipids, exacerbates this issue, resulting in reduced process performance. Therefore, successful design of an RO system for ABE separation from fermentation broth requires a thorough assessment of broth composition, ABE properties, system operating parameters, target separation efficiency, energy consumption, and overall economic implications. Proper pretreatment of fermentation broths and the integration of hybrid technologies, such as combining adsorption, pervaporation, or liquid-liquid extraction with RO, are anticipated to play a substantial role in facilitating large-scale ABE removal and concentration from bioreactors. Overall, RO has great potential to be an economically viable process for separation of butanol from fermentation reactors.