Flexibility as the Key to Stability: Optimization of Temperature and Gas Feed during Downtime towards Effective Integration of Biomethanation in an Intermittent Energy System

Biological methanation is the production of CH4 from CO2 and H2. While this approach to carbon capture utilization have been widely researched in the recent years, there is a gap in the technology. The gap is towards the flexibility in biomethanation, utilizing biological trickling filters (BTF). With the current intermittent energy system, electricity is not a given surplus energy which will interfere with a continuous operation of biomethanation and will result in periods of operational downtime. This study investigated the effect of temperature and H2 supply during downtimes, to optimize the time needed to regain initial performance. Short (6 h), medium (24 h) and long (72 h) downtimes were investigated with combinations of three different temperatures and three different flow rates. The results from these 27 experiments showed that with the optimized parameters, it would take 60 min to reach 98.4% CH4 in the product gas for a short downtime, whereas longer downtimes needed 180 min to reach 91.0% CH4. With these results, the flexibility of biomethanation in BTFs have been proven feasible. This study shows that biomethanation in BTFs can be integrated into any intermittent energy system and thereby is a feasible Power-2-X technology.