High Pressure Moving Bed Biofilm Reactor for Syngas Fermentation

Abstract

Two well-studied strategies to enhance syngas fermentation are elevated headspace pressure, increasing gas-liquid (GL) mass transfer, and moving bed biofilms (MBB) to overcome kinetic growth limitation. A combination of these two methods has not received much attention. This study evaluates the integration of these two strategies in one single reactor. The hydrogen (H2) GL mass transfer is the primary bottleneck in syngas fermentation due to the lowest solubility among syngas components. The syngas composition is mimicked here as a mixture of H2 gas and sodium bicarbonate (NaHCO3) salt. Initially, fermentation is performed at 15 bar H2 headspace pressure in the suspended culture, then the experiment is repeated with MBB integration, and the performance is critically evaluated. The study with integrated biofilm shows a 33 % improvement in H2 gas uptake rate (200 mmol/L·day) and 48 % enhancement in acetate synthesis rate (37.4 mmol/L· day). This study concludes that MBB could successfully be integrated into an elevated pressure syngas fermenter, enhancing the fermentation process efficiency.