Enhancement of dark fermentative H-2 production by gas separation membranes: A review

Biohydrogen production via dark fermentation is currently the most developed method considering its practical readiness for scale-up. However, technological issues to be resolved are still identifiable and should be of concern, particularly in terms of internal mass transfer. If sufficient liquid-to-gas H-2 mass transfer rates are not ensured, serious problems associated with the recovery of biohydrogen and consequent inhibition of the process can occur. Therefore, the continuous and effective removal of H-2 gas is required, which can be performed using gas separation membranes. In this review, we aim to analyze the literature experiences and knowledge regarding mass transfer enhancement approaches and show how membranes may contribute to this task by simultaneously processing the internal (headspace) gas, consisting mainly of H-2 and CO2. Promising strategies related to biogas recirculation and integrated schemes using membranes will be presented and discussed to detect potential future research directions for improving biohydrogen technology.