Assessment of the performance of packing materials in trickle bed reactors for efficient biomethanation

Selecting the optimal packing material is pivotal for enhancing biological methanation in Trickle Bed Reactors (TBRs). This research compares the performance of three packing materials: Raschig rings, carbon pellets, and biochar, focusing on the resulting process efficiency, stability and the microbial community structure within the reactors. Among the evaluated materials, Raschig rings demonstrated superior methanation performance, achieving one of the highest methane production rates (12.7 LCH4/LR d), presenting stable pH levels and a notable increase of Volatile Fatty Acids (VFAs) concentration (1.7 g/L). In contrast, the carbon pellets exhibited lower methanation efficiency, whereas the biochar, while promising, implicated significant technical challenges. Effective pH stabilization was linked to the regulation of bicarbonate and ammonia equilibrium. Furthermore, the reduced presence of Methanothermobacter marbugensis , as observed at higher gas loading rates, correlated well with the diminished conversion efficiency in the bioreactors, utilizing carbon pellets and biochar as packing materials.