Optimized biological CO2-methanation with a pure culture of thermophilic methanogenic archaea in a trickle-bed reactor

In this study, a fully automated process converting hydrogen and carbon dioxide to methane in a high temperature trickle-bed reactor was developed from lab scale to field test level. The reactor design and system performance was optimized to yield high methane content in the product gas for direct feed-in to the gas grid. The reaction was catalyzed by a pure culture of Methanothermobacter thermoautotrophicus IM5, which formed a biofilm on ceramic packing elements. During 600 h in continuous and semi-continuous operation in countercurrent flow, the 0.05 m3 reactor produced up to 95.3 % of methane at a methane production rate of 0.35 m3CH4 mg3h- 1. Adding nitrogen as carrier gas during startup, foam control and dosing of ammonium and sodium sulfide as nitrogen and sulfur source were important factors for process automation.

Automated summary

The study developed a fully automated process to convert hydrogen and carbon dioxide to methane in a high temperature reactor, achieving high methane content in the product gas for direct feed-in to the gas grid. Optimization of reactor design and system performance led to successful production of methane at a high rate using a specific culture as catalyst.