(400f) Process Intensification in Biofuels Manufacturing Integrating Membrane Solvent Extraction (MSE) with Bioprocessing and Conventional Distillation Systems

Ethanol is still a leading biofuel manufactured in the U.S. with about 15 billion gallons per year in 2019. Even though progress is being made in second generation cellulosic biofuels, first generation corn starch-based ethanol is still the leading biofuel in the U.S. Despite the advantages of using corn starch-based biofuel as a blend with gasoline, there continues to remain opportunities for improving the cost and energy performance, water use and environmental impacts of corn ethanol manufacturing.

In conventional biofuels manufacturing, distillation continues to be the major separation and purification process for concentrating ethanol from the dilute fermentation broth. This requires a significant amount of capital and operating costs including energy cost and water use. Here we present the use of in-situ membrane solvent extraction of fermentation broth integrated with the current process as an effective way of ethanol separation. Membrane solvent extraction offers significant advantages compared to conventional liquid-liquid extraction including eliminating the formation of emulsions, ability to use solvents that have potential toxicity to microorganisms at higher concentrations, ease of separation by using high boiling solvents. One approach is to have the fermentation broth continuously taken through a membrane module with the broth getting in contact with extraction solvent at the membrane interface. The extracted ethanol and the solvent can then be separated, and the ethanol can be concentrated further to achieve desired final purity. The purified solvent is recycled and reused back in the MSE process. The fermentation broth, after extraction, with less ethanol concentration is then returned to the fermenter to achieve further acceleration of the fermentation process and to minimize inhibitory effects of higher ethanol concentration during fermentation.

A detailed process model of the above process including membrane solvent extraction was developed using ASPEN Hysys and compared with conventional distillation systems. MSE with recycle was shown to be very effective in integrating with conventional biofuel manufacturing reducing the operating costs, energy use and water use. This also has additional benefits in accelerating the fermentation process resulting in better yields and better productivity. All of this together, can result in more competitive and environmentally sustainable biofuels manufacturing. MSE integrated with bioprocessing and conventional separation technologies can also be explored in other process industries.