Methane oxidation in landfill cover soils, is a 10% default value reasonable?
Received for publication May 10, 2008. We reviewed literature results from 42 determinations of the fraction of methane oxidized and 30 determinations of methane oxidation rate in a variety of soil types and landfill covers. Both column measurements and in situ field measurements were included. The means for the fraction of methane oxidized on transit across the soil covers ranged from 22 to 55% from clayey to sandy material. Mean values for oxidation rate ranged from 3.7 to 6.4 mol m–2 d–1 (52–102 g m–2 d–1) for the different soil types. The overall mean fraction oxidized across all studies was 36% with a standard error of 6%. The overall mean oxidation rate across all studies was 4.5 mol m–2 d–1 ± 1.0 (72 ± 16 g m–2d–1). For the subset of 15 studies conducted over an annual cycle the fraction of methane oxidized ranged from 11 to 89% with a mean value of 35 ± 6%, nearly identical to the overall mean. Nine of these studies were conducted in north Florida at 30° N latitude and had a fraction oxidized of 27 ± 4%. Five studies were conducted in northern Europe (~50–55° N) and exhibited an average of 54 ± 14%. One study, conducted in New Hampshire, had a value of 10%. The results indicate that the fraction of methane oxidized in landfill greater than the default value of 10%. Of the 42 determinations of methane oxidation reported, only four report values of 10% or less.