Landfill Methane Oxidation Response to Vegetation, Fertilization, and Liming

Abstract

Abstract This study was conducted to evaluate the effects of vegetation, N fertilizers, and lime addition on landfill CH 4 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 CH 4 by 47 and 37%, respectively, at peak uptake; but the rate for both treatments was about 18% at steady slate. Nitrate and NH 4 amendments induced a more rapid onset of CH 4 oxidation relative to KCl controls. However, at steady state, NH 4 inhibited CH 4 oxidation in bare columns but not in grassed columns. Nitrate addition produced no inhibitory effects. Lime addition to the soil consistently enhanced CH 4 oxidation. In all treatments, CH 4 consumption increased to a peak value, then declined to a lower steady‐state value; and all gassed columns developed a pH 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 CH 4 uptake, but there is no evidence that the inhibition persists. The ability of vegetation to mitigate NH 4 inhibition indicates that results from bare‐soil tests may not always generalize to vegetated landfill caps.