Air-gap membrane distillation for the separation of bioethanol from algal-based fermentation broth

More than 80% of the energy consumed in the world comes from fossil fuels alone. However, fermentative production of bioethanol has recently gained a considerable interest as an alternative and renewable fuel. Among the different biomasses, the use of macro-algae hydrolysate as the fermentation substrate has been shown to be interesting. However, after fermentation, ethanol has to be separated from the complex broth containing numerous compounds such as microorganisms, fermentation co-products, non-fermentable organic matter, salts, etc. In this study, Air-Gap Membrane Distillation (AGMD) was evaluated to extract ethanol from these complex mixtures. Experiments were conducted using synthetic mixtures and real algal-based fermentation broths. AGMD was able to obtain an ethanol-enriched permeate while other compounds were retained by the membrane. Furthermore, by adjusting the operating parameters, it was possible to maximize the process productivity and selectivity at the same time. Finally, working with the real biofluids revealed that AGMD operation was robust toward membrane wetting, even in presence of membrane fouling. AGMD was thus demonstrated to be a suitable technique for bioethanol extraction from algal-based fermentation broths.