Quantifying Methane Oxidation from Landfills Using Stable Isotope Analysis of Downwind Plumes

Abstract

Landfills are major contributors to the atmospheric CH4 budget. A major uncertainty in estimating CH4 flux from landfills is determining the attenuation of CH4 emission by methanotrophic bacteria in the aerobic outer portions of the cover soil. These bacteria intercept the gas as it migrates toward the atmosphere. To estimate cover soil oxidation, we made seasonal measurements of the difference in the δ13C of CH4 within the anoxic zone and CH4 released from landfills and captured downwind at two landfills in the Northeastern United States. Anoxic zone CH4 at the Nashua Landfill averaged −54.6 ± 0.7‰, n = 205, and displayed no significant seasonal pattern. Methane was in excess over ambient air concentrations in the downwind plume ranging from 2.13 to 3.41 ppmv. The δ13C of excess CH4, as determined by mass balance with correction for ambient air CH4, varied from −49.35 to −54.28‰. We used these values to calculate soil CH4 oxidation, which ranged from 0 to 23.6%. Oxidation was greatest in the summer and in the fall, with an annual value of 12 ± 8%. At a second landfill, plume CH4 ranged from 1.96 to 2.92 ppmv with excess δ13C values of −52.17 to −58.06‰. Oxidation at this landfill ranged from 0 to 14%.

Elimination of methane generated from landfills by biofiltration: a review

“…This idea comes from the fact that some bacteria are able to degrade air pollution compounds, such as CH 4 . This process already provides for the elimination of some 10-100% of the CH 4 escaping from the upper layers of landfills, depending on local climatic conditions (Nozhevnikova et al 1993;Kightley et al 1995;Czepiel et al 1996;Chanton et al 1999;Christophersen et al 2000;Bajic and Zeiss 2001;EPA 2005;Stralis-Pavese et al 2006).…”

“…During winter, the CH 4 conversion within landfill covers is reduced to around 3-10% (Chanton et al 1999;Chanton and Liptay 2000;Giani et al 2002;Spokas et al 2006). However, at an ambient temperature of 2°C, Christophersen et al (2000) have noted that it was still possible to biodegrade all of the CH 4 produced in older landfills if IL is inferior to 70 g m -2 d -1 .…”

Biodegradation of Trace Gases in Simulated Landfill Soil

“…4 -6 Field studies have shown that between 10 to 100% of the emitted methane can be oxidized on an annual basis. [7][8][9] Furthermore, methane flux emission measurements have shown negative fluxes, indicating uptake of atmospheric methane and proving that in some cases, landfill cover soils may even serve as sink for atmospheric methane. 10 -12 Although attenuation of methane in landfill covers has been intensively studied to evaluate the contribution of landfills to global warming, there is little research concerning the potential for attenuation of VOCs.…”

Seasonal Variability in CH4Emissions from a Landfill in a Cool, Semiarid Climate

“…7,[9][10][11][12] This conclusion is supported by stable isotopic measurements of carbon in the emitted CH 4 . 13,14 The work of these authors suggests that perhaps the landfill CH 4 contribution to the atmospheric cycle had been significantly overestimated. However, seasonal aspects of the balance between landfill CH 4 emissions and methanotrophic consumption in cover soils needed further consideration.…”