Characterization of the biofiltration of methane emissions from municipal anaerobic effluents

Atmospheric methane emissions from anaerobic effluents represent a source of greenhouse gases that can be mitigated by biofiltration. This study performs a comprehensive analysis on methane biofiltration using compost as packing to determine the limiting phenomena. A mathematical model calibrated by heterogeneous respirometry predicted the temperature effects (15-40 degrees C) on the kinetics of mass transport and biological reaction in a methanotrophic biofilm. It was validated through experimentation from steady state continuous runs (elimination capacities from 38 to 50 g M-3 h(-1) with removal efficiencies of 62-80%). Results from model validation showed no significant differences (p-value 0.05) between the experimental methane elimination capacities and those predicted by the model at inlet 21 g(cH4) m(-3) (4% volume in air, at 20 degrees C and 0.78 atm). To assess the limiting phenomena, the global and biofilm effectiveness factors were evaluated. This analysis demonstrated a biofilm limitation, specifically due to methane diffusion within the biofilm at the conditions tested (19 min of empty bed residence time). Even if the optimal temperature for methane oxidation activity was between 25 and 30 degrees C, the lower reaction rates at other temperatures did not limit the methane biofiltration in the applied interval.