Evaluating Methane Oxidation Efficiencies in Experimental Landfill Biocovers by Mass Balance and Carbon Stable Isotopes
2012
Capanema, Marlon A. | Cabral, Alexandre R.
Biocovers are an alternative for mitigating fugitive and residual emissions of methane from landfills. In this study, we evaluated the performance of two experimental passive methane oxidation biocovers (PMOBs) constructed within the existing final cover of the St-Nicéphore landfill (Quebec, Canada). The biocovers were fed in a controlled manner with raw biogas and surface fluxes were obtained using static chambers. This enabled calculating mass balances of CH₄ and oxidation efficiencies (f ₒ_MB). Most of the time, f ₒ_MB ≥ 92 % were obtained for loadings as high as 818 g CH₄ m⁻² day⁻¹ (PMOB-2) and 290 g CH₄ m⁻² day⁻¹ (PMOB-3B). The lowest efficiencies (f ₒ_MB = 45.5 % and 34.0 %, respectively) were obtained during cold days (air temperature ~0 °C). Efficiencies were also calculated using stable isotopes (f ₒ_SI); the highest f ₒ_SI were 66.4 % for PMOB-2 and 87.3 % for PMOB-3B; whereas the lowest were 18.8 % and 23.1 %, respectively. However, f ₒ_SI values reflect CH₄ oxidation up to a depth of 0.10 m, which may partly explain the difference in regards to mass balance-derived efficiencies. Indeed, it is expected that a significant fraction of the total CH₄ oxidation occurs within the zone near the surface, where there is greater O₂ availability. The influence of the values of fractionation factors α ₒₓ and α ₜᵣₐₙₛ were also evaluated in this paper.
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