Effect of landfill cover layer modification on methane oxidation.

Levels of methane (CH4) oxidation in materials used for landfill cover attained in the laboratory are not often replicated in the field due to effects from the surrounding environment. This study investigates the three dominant factors affecting CH4 oxidation in the cover layer, namely, the thickness of cover layer, the methanotroph spraying manner, and the osmotic coefficient of the cover material. Results show that improved CH4 emission performance of the cover layer can be realized if methanotroph are introduced, meaning that a thinner cover layer is required. The highest CH4 emission reduction can be realized by spraying methanotroph into the top, middle, and bottom layers of a 30-cm thick cover layer with an osmotic coefficient of 7.76 × 10-5 cm s-1. Comparing results on cover layer thickness, methane monooxygenase (MMO) activity was much lower with increasing thickness meaning that the thicker cover could reduce O2 availability, thus inhibiting MMO activity. This suggests that MMO may be responsible for differences in CH4 emission reduction and/or oxidation making the osmotic coefficient an important factor for cover layer material.