Effects of Leachate Irrigation on Landfill Vegetation and Subsequent Methane Emissions

Short-rotation tree forests are irrigated with landfill leachate to reduce both leachate volume and nutrient content. It is of interest both for leachate treatment and energy recovery to optimise the productivity of such plantations. This study's aim was to investigate the effects of irrigation on soil quality, tree growth and on emissions of landfill gas (LFG) produced in the wastes. Soils irrigated with leachate had a higher average nutrient and organic matter contents, and a lower dry solids content. Larger trees occur on plots irrigated with leachate, presumably due to the positive effect of water and nutrient supply. The willows used in this experiment seemed to be tolerant of high carbon dioxide concentrations, as no statistically effect arising from LFG emissions could be linked to tree growth. Methane oxidation levels between 50 and 950 mol m^-2 yr^-1 were observed. The positive correlation between soil methane oxidation capacity and tree presence is an interesting perspective on reduction of methane emissions by landfill's top cover vegetation type. Optimising methane oxidation using vegetation as a ‘cover crop’ could reduce the amount of methane discharged into the atmosphere.