Integration of two trickle-bed reactors in series for enhanced biomethane production from syngas

Biomethanation using trickle-bed reactors offers a viable solution for converting syngas from gasification or pyrolysis to methane. Under the power-to-methane concept, extraneous hydrogen is added to increase methane yield. However, optimizing the bioconversion to meet high methane purity remains a challenge. This study addresses this gap by evaluating a novel reactor configuration consisting of two thermophilic trickle-bed reactors in series. The first reactor in the series was inoculated and enriched to convert carbon monoxide completely. The second reactor was enriched to convert carbon dioxide and externally added hydrogen to methane. This approach was compared with a single reactor configuration, where extraneous hydrogen is added in the first reactor. The series configuration achieved 100% carbon monoxide conversion, 95% methane purity, and a methane production rate of 6.13 Nm3·m-3·d-1. The single reactor configuration achieved a methane production rate of 4.64 Nm3·m-3·d-1 with conversion and purity on par with the series configuration. The two reactors in series offer a more flexible configuration for use with real syngas and operation under a variable hydrogen supply in the context of power-to-methane.