Hydrogenotrophic methanogenic granular sludge formation for highly efficient transforming hydrogen to CH4.

This paper presents a potential process that can enhance H2 transformation to CH4 and simultaneously upgrading biogas by using hydrogenotrophic methanogens. For the first time, anaerobic granules were developed in upflow anaerobic sludge blanket (UASB) reactor feeding H2/CO2 syngas as the sole substrate and the granule characterization was thoroughly investigated. The results from experiment revealed that the H2 consumption rates of UASB reactor increased from 32.2 mmol L-1·d-1 at H2 feeding rate 0.08 g L-1·d-1 to 132.0 mmol L-1·d-1 at 0.37 g L-1·d-1, indicating that the hydrogenotrophic methanogenesis pathway was stimulated by injection of H2. Abundant cavities and cracks were observed on the surface and cross-section of granules, which greatly facilitated internally transferring H2/CO2 synthesis gas and biogas escape. The abundance of hydrogenotrophic Methanobacterium increased, while Methanosaeta, Methanosarcina, and Methanomassiliicoccus decreased with increasing H2 feeding rate. In general, this paper offers a feasible solution in terms of energy transformation and connecting power to fuel.