Biogas upgrading in a pilot-scale trickle bed reactor - Long-term biological methanation under real application...

The biological methanation of H₂ and CO₂ in trickle bed reactors is one promising energy conversion technology for energy storage, but experiences at pilot-scale under real application conditions are still rare. Therefore, a trickle bed reactor with a reaction volume of 0.8 m³ was constructed and installed in a wastewater treatment plant to upgrade raw biogas from the local digester. The biogas H₂S concentration of about200 ppm was reduced by half, but an artificial sulfur source was required to completely satisfy the sulfur demand of the methanogens. Increasing the ammonium concentration to > 400 mg/L was the most successful pH control strategy, enabling stable long-term biogas upgrading at a CH₄ production of 6.1 m³/(m³_RV·d) with synthetic natural gas quality (CH₄ > 98%). The results of this study with a reactor operation period of nearly 450 days, including two shutdowns, represents an important step towards the necessary full-scale integration.