EVALUATION OF METHANE EMISSIONS FROM AN EXPERIMENTAL LANDFILL OF SOLID WASTE IN MURIBECA /PE-BRAZIL

Abstract

The landfill gas (LFG) generated in Municipal Solid Waste (MSW) landfills can be emitted to the atmosphere through the gas collection system or by its escape through the final cover layer. The objective of this paper is to present the preliminary results of the methane (CH4) superficial emissions investigation at three different cover layers in an experimental cell, located at Muribeca Landfill, Recife/PE. The static flux chamber methodology was used in order to evaluate CH4 emissions “in situ”, which was associated with laboratory tests for soil characterization. Eight flux chamber tests for measuring CH4 emission, as well as four tests for biogas concentrations along the cover layer depth were done to evaluate CH4 retention and/or oxidation. They were performed from September to December/2008. The CH4 flux in the capillary cover layer (BAC) was 0.37 Nl/m2.h, in the methanotrophic layer (MET) was 1.90 Nl/m2.h, and in the conventional layer (CONV) was 4.97 Nl/m2.h. The lowest CH4 flux determined in the BAC layer was related to the gas distribution layer at the bottom of this cover that equalized gas pressure and concentration before its passage through the soil. It was also verified that CH4 volumetric concentration and the relation CO2/CH4 increased from the bottom to the top of all cover layers. This behavior was more accentuated at the methanotrophic layer, which was an indication of CH4 oxidation. The study of alternative cover layers and its physical-chemical and constructive properties to reduce CH4 emissions and prevent pollution to the atmosphere is extremely important for most small and medium sized landfills in Brazil, where the recovery of LFG is incipient and unviable.

Key Words: solid waste, landfill, biogas, final cover layer.