Extractive Ethanol Fermentation with Ethanol Recovery by Absorption in Open and Closed Systems

Abstract

Conventional ethanol production has limitations, including substrate and product inhibitions, which increase both energy requirements for ethanol recovery and vinasse generation. Extractive fermentation, which removes ethanol as it is produced within the fermentation vat, offers an effective alternative to reducing the inhibitory effects in conventional processes. However, an efficient method for recovering the extracted ethanol is also crucial. Thus, this study investigated an alternative ethanol production process using extractive ethanol fermentation integrated with ethanol recovery by absorption in both open and closed systems, specifically, comparing scenarios with and without CO2 recirculation produced during fermentation. The recovery system used two absorbers connected in series using monoethylene glycol (MEG) as an absorbent. Under extractive fermentation conditions without CO2 recirculation, the conversion of 300.0 g L−1 of substrate resulted in a total ethanol concentration of 135.2 g L−1, which is 68% higher than that achieved in conventional fermentation (80.4 g L−1). The absorption recovery efficiency reached 91.6%. In the closed system, with CO2 recirculation produced by fermentation, 280.0 g L−1 of substrate was consumed, achieving ethanol production of 126.0 g L−1, with an absorption recovery percentage of 98.3%, similar to that of industrial facilities that use a gas scrubber tower. Additionally, the overall process efficiency was close to that of conventional fermentation (0.448 gethanol gsubstrate−1). These results highlight the potential of this alternative process to reduce vinasse volume and energy consumption for ethanol recovery, lowering total costs and making it a viable option for integrated distilleries that combines ethanol production with other related processing operations.