Landfill methane oxidation response to vegetation, fertilization, and liming

This study was conducted to evaluate the effects of vegetation, N fertilizers, and lime addition on landfill CH4 oxidation. Columns filled with compacted sandy loam and sparged with synthetic landfill gas were used to simulate a landfill cover. Grass-topped and bare-soil columns reduced inlet CH4 by 47 and 37%, respectively, at peak uptake; but the rate for both treatments was about 18% at steady state. Nitrate and NH4 amendments induced a more rapid onset of CH4 oxidation relative to KCl controls. However; at steady state, NH4 inhibited CH4 oxidation in bare columns but not in grassed columns, Nitrate addition produced no inhibitory effects. Lime addition to the soil consistently enhanced CH4 oxidation. In all treatments, CH4 consumption increased to a peak value, then declined to a lower steady-state value; and all gassed columns developed a pa gradient Neither nutrient depletion nor protozoan grazing could explain the decline from peak oxidation levels. Ammonium applied to grassed cover soil can cause transient reductions in CH4 uptake, but there is no evidence that the inhibition persists. The ability of vegetation to mitigate NH4 inhibition indicates that results from bare-sop tests may not always generalize to vegetated landfill caps.