Can soil gas profiles be used to assess microbial CH4 oxidation in landfill covers?

Abstract

A method is proposed to estimate CH(4) oxidation efficiency in landfill covers, biowindows or biofilters from soil gas profile data. The approach assumes that the shift in the ratio of CO(2) to CH(4) in the gas profile, compared to the ratio in the raw landfill gas, is a result of the oxidation process and thus allows the calculation of the cumulative share of CH(4) oxidized up to a particular depth. The approach was validated using mass balance data from two independent laboratory column experiments. Values corresponded well over a wide range of oxidation efficiencies from less than 10% to nearly total oxidation. An incubation experiment on 40 samples from the cover soil of an old landfill showed that the share of CO(2) from respiration falls below 10% of the total CO(2) production when the methane oxidation capacity is 3.8 μg CH(4)g(dw)(-1)h(-1) or higher, a rate that is often exceeded in landfill covers and biofilters. The method is mainly suitable in settings where the CO(2) concentrations are not significantly influenced by processes such as respiration or where CH(4) loadings and oxidation rates are high enough so that CO(2) generated from CH(4) oxidation outweighs other sources of CO(2). The latter can be expected for most biofilters, biowindows and biocovers on landfills. This simple method constitutes an inexpensive complementary tool for studies that require an estimation of the CH(4) oxidation efficiency values in methane oxidation systems, such as landfill biocovers and biowindows.

Pore-gas dynamics in overburden and reclamation soil covers

“…Microbial CH 4 oxidation and microbial respiration are simultaneous processes contributing to the production of CO 2 . The contribution of respiration decreases significantly with increasing rates of CH 4 oxidation (Gebert 2011b). Therefore, observations that O 2 consumption and CO 2 production were higher at lower rates of CH 4 oxidation are likely attributed to additional consumption of O 2 and production of CO 2 by microbial respiration.…”

“…The relationship between soil moisture and CH 4 oxidation has been researched extensively for landfill cover soils and has been found to strongly correlate to CH 4 oxidation Reeburgh 1996, Bogner 1997 CH 4 diffusivity at high moisture contents Moldrup 1996;Borjesson and Svensson 1997;De Visscher and Van Cleemput 2003;Aachib et al 2004;Molins et al 2008;Gebert et al 2011) and physiological stresses to microbial populations at low moisture contents (Whalen et al 1990;King 1997;Borjesson 2004).…”

The effects of aged refuse and sewage sludge on landfill CH4 oxidation and N2O emissions: Roles of moisture content and temperature

“…Additionally, changing the mix ratios of the aged refuse and sewage sludge can be used to regulate grain diameter, which influences gas vertical speed and thus the MOP (Gebert et al, 2011).…”

Aerobic processes in landfill: an Australian field trial

“…Studies of aerobic degradation in landfills have largely focussed on CH4 oxidation within soil and bio-covers, with current methods including mass balance (Bogner and Spokas, 1993), stable isotopes (Liptay et al, 1998) and concentration ratios (Christophersen et al, 2000, Gebert et al, 2011b, Pratt et al, 2013. There has been no attempt to measure both CH4 oxidation and composting in the waste layer immediately beneath the cover.…”

“…There are three established techniques for estimating the efficiency and capacity of CH4 oxidation in landfill covers including carbon mass balance (Bogner and Spokas, 1993), concentration ratio (Christophersen et al, 2000, Gebert et al, 2011b, Pratt et al, 2013 and stable isotope analysis (Liptay et al, 1998). Each of these techniques are discussed critically in the following sections.…”