Effect of minimizing carrier irrigation on H2 conversion in trickle bed reactors during ex situ biomethanation

Abstract Biological methanation of renewable H2 and CO2 has been projected to have considerable potential in future energy systems by coupling power and gas energy infrastructures. A suitable technology to facilitate the biological methanation is the ex-situ trickle bed reactor in which a methanogenic biofilm produces CH4 from H2 and CO2. Biofilm irrigation constitutes a critical element for reactor control and has previously been shown to both enhance and decrease reactor performance. In this study, an improvement in the H2 conversion rate of 53% was demonstrated when changing the interval between sprinklings from 1 to 7 days. The results demonstrate a minimal requirement for nutrient supply to support biological activity and underlines that carrier irrigation not only impairs H2 conversion at short-term due to increases in mass transfer resistance, but also induces longer-term effects on process performance. Three potential mechanisms underlying the physicochemical and biological effects from carrier irrigation are discussed.