Load change capability of an anaerobic thermophilic trickle bed reactor for dynamic H₂/CO₂ biomethanation

Increasing shares of energy production originating from fluctuating renewable sources require measures that are able to balance power production for a stable electricity grid. H₂/CO₂ biomethanation is a suitable approach to convert fluctuating excess renewable energy into the storable substitute natural gas. This study investigated the rapid load change capability of an anaerobic thermophilic trickle bed reactor while maintaining a high methane content. The return to full load (62.1 m³_H2/m³_{trickle bed}/d) after a 30-min operational off-cycle was possible almost immediately, while 24-h interruptions required a 60-min stepwise load increase. To accelerate this delayed microbial conversion activity, non-steady state substrate gas conversion can be controlled via substrate and product gas flow rates, allowing to reactivate the entire microbial community and produce high quality product gas. Reactor design might be further improved to avoid short-circuiting and use the entire trickle bed gas phase as high quality gas buffer during initial load increases.