Accessible sampling methodologies to quantify the net methane emission from landfill cells

Abstract

Landfills are one of the main sources of anthropogenic methane (CH4) emissions in urban areas. The environmental conditions specific to each locality, the waste management and the infrastructure of each landfill will influence the emissions of this gas. By applying different methodologies, this study aims to investigate the total contribution of CH4 to the atmosphere from a landfill, as well as the surface fluxes within the cells and the passive gas vents. According to the results, mean atmospheric CH4 concentrations from landfills were measured up to 6 ppm higher than those recorded in urban areas and locations distant from CH4 fixed sources. Two closed cells were selected to study surface fluxes by static chamber technique. CH4 uptake (1.65E-08 to 2.04E-06 g m− 2 d− 1 ) was recorded in between 60% and 87.5% of the chambers, indicating that the surface acted as a sink for the gas, as compared to the mean uptake observed from a control site (1.72E-06 g m-2 d− 1 ). CH4 emissions from gas vents were studied using a tracer technique with permeable capsules, a methodology used for the first time in a landfill. Relatively high emissions were detected, up to 1.20E+04 g d− 1 . Finally, from the net CH4 emission calculated, the energy produced if the emitted CH4 were captured was estimated to be 3.23 GJ. The results highlight the importance of these studies for decision-makers to plan future landfill infrastructure adequately, implement mitigation measures to reduce emissions of this potent greenhouse gas and contribute to the energy system resources.