Thin biocovers for methane emission mitigation.

摘要

Landfills operated as a bioreactor landfill emit methane and carbon dioxide when leachate or liquids are added. These early emissions are characterized by small volumes of methane that increase as landfilling proceeds to over 100 g CH4/m2 d. Emissions from early landfilling are located in hotspots and are not evenly spread out over the surface. This research presents the possibility of controlling these emissions by using the intermediate cover in a landfill as a methane control barrier or biocap. The main mechanism involved is methanotrophy, or biological oxidation of methane by methanotrophic bacteria. Consequently, these covers have been coined intermediate thin biocovers (TBC). Performance of compost-based TBC has shown to oxidize methane in the field, even during mild winter months when it is assumed that methanotrophic bacteria become less active. 100% of the flux passing through the TBC can be oxidized. However, compost must be stable or mature. Stability impacts methane oxidation due to competition for water, nutrients and oxygen. The TBC, once the landfill has been capped, can act as a barrier and promote lateral migration of leachate. Compression of compost and its impact on hydraulic conductivity were evaluated. An equation to relate compression and hydraulic conductivity is proposed using an exponential function. Lateral migration in a landfill where intermediate covers are used will depend on the compression and consequently the ratio of hydraulic conductivity of the waste and the intermediate cover. Lateral migration gradient is used to describe this phenomenon. The lateral migration gradient was found to be 517m/degree.