Direct Measurement of Methane Emission Rates: Multiyear Application to a Municipal Landfill in Southern Italy

Abstract

Municipal Solid Waste (MSW) landfills have been identified as one of the most important sources of methane (CH4) emission. MSW contains a certain amount of biodegradable organic matter which undergoes anaerobic degradation resulting in the production of the landfill gas (LFG), which main component is tipically represented by CH4. In order to minimise its negative effects on the envi-ronment, LFG recovery is a suitable tool to control CH4 emissions from a landfill site and the measurement of CH4 emissions represents a good way to evaluate the effectiveness of LFG recover-ing system in reducing biogas emission to the atmosphere. However, up to now few measurements of landfill CH4 emissions have been reported, due to the heterogeneity of waste composition and temporarily landfill surface covering which give as a result high spatial variability of the LFG emis-sion from the landfill surface. The main aim of the present study was to evaluate CH4 diffuse emis-sions, based on direct measurements carried out at Palermo (IT) landfill by means of a flux accumu-lation chamber coupled with a flame ionization detector (FID). The field campaign was carried out over a period of two years, and it was split into several experimental phases, performed in different seasons, in order to evaluate the influence that specific landfill features have on CH4 emissions, as well as to understand the influence exterted by meteorological conditions during the field cam-paigns. Through the use of a geostatistic methodology, the instantaneous CH4 fluxes from the land-fill surface have been used to obtain the total amount of methane emitted from the investigated area as well as the methane flux maps. Such emissions were further compared with the estimate achieved by means of CH4 mass balance equations. The obtained results showed that a relationship between the local CH4 emissions and some specific features of landfill can be established, and that the emis-sions obtained by applying the flux accumulation chamber method are in good agreement with the ones derived by the application of mass balance equations, also suggesting that the contoured flux maps represent a reliable tool to locate areas with abnormal emission in order to improve the gas re-covery system efficiency.