DESIGN, IMPLEMENTATION AND OPERATION OF SOIL-BASED METHANE OXIDATION WINDOWS FOR THE REMEDIATION OF GAS EMISSION HOTSPOTS IN LANDFILL COVER SOILS

摘要

Microbial oxidation of CH4 in landfill cover soils can effectively reduce climate-relevant emissions. In general, the oxidation potential of natural soils is sufficient for the conversion of low methane fluxes typically produced in the waste body of unsealed old landfills. However, landfill gas flux through the cover often is not evenly distributed, but escapes through preferential flow paths. Eight of these emission hotspots were remediated on an old landfill in northern Germany. The rationale of the remediation measure was i) to distribute the prevailing methane flux to an area sufficiently large to reduce the methane load to a level which does not exceed the oxidation potential of the soil material and ii) to enhance the soil gas diffusivity and thus the ingress of atmospheric oxygen required for the oxidation process. Three alternative designs of soil-based methane oxidation windows have been developed for the remediation of these emission hotspots (Figure 1). The basic principle is to achieve a uniform gas distribution, either by solely breaking up existing preferential flow paths (G3), or by additionally applying a gas distribution layer (GDL) (G1-2). An increase in air filled porosity was to be achieved by low compaction (all), and choice of adequate soil material for the methane oxidation layer (MOL) (G1-2).