Abstract
<jats:p> Methane CH <jats:sub>4</jats:sub> biofiltration is a promising approach for mitigating dilute emissions, but long-term performance remains difficult to predict because transport limitations and microbial succession are tightly coupled. In this study, replicated compost–woodchip biofilters were used to link operating conditions with CH <jats:sub>4</jats:sub> removal performance and metagenomic evidence of CH <jats:sub>4</jats:sub> oxidation. Nine packed-bed columns were operated under three inlet CH <jats:sub>4</jats:sub> concentrations (5000, 10000, and 25000 ppmv) and two gas flow rates (1 and 2 L min <jats:sup>-1</jats:sup> ). Biofilters rapidly established \ce{CH4} oxidation activity but consistently declined from peak to lower sustained performance. At 1 L min <jats:sup>-1</jats:sup> , the maximum removal efficiency reached 89.1% at 5000 ppmv, whereas higher inlet concentrations increased the elimination capacity but reduced the removal efficiency. At 2 L min <jats:sup>-1</jats:sup> , removal efficiencies were lower (10-40%), consistent with reduced empty bed residence time. Metagenomic analysis of the 1 L min <jats:sup>-1</jats:sup> operation showed that the compost-derived community remained diverse while shifting over time. Methanotroph-associated families, dominated by <jats:italic toggle="yes">Methylococcaceae</jats:italic> , increased above the initial compost baseline and showed bed position-dependent enrichment. Genome-resolved analysis recovered two high-quality methanotroph MAGs, <jats:italic toggle="yes">Methylobacter marinus</jats:italic> and <jats:italic toggle="yes">Methylocaldum szegediense</jats:italic> , while functional profiling showed enrichment of particulate methane monooxygenase and downstream C1-processing genes. Together, these results indicate that CH <jats:sub>4</jats:sub> biofilter performance was governed by the coupling between engineering transport constraints and microbial succession. Gas residence time and inlet loading shaped the efficiency--capacity trade-off, while broader mass-transfer and packed-bed limitations likely constrained sustained removal even when methanotroph-associated taxa and CH <jats:sub>4</jats:sub> oxidation genes persisted. </jats:p>