Comparison between Field and Laboratory Methane Oxidation Rates

As part of a field study aiming at evaluating the efficiency of a mixture of coarse materials (sand and gravel) with compost to oxidize fugitive CH₄ emissions, column tests were performed and the results were compared to field values obtained from an experimental biocover where the CH₄ loading was controlled. Three oxidation tests were performed with samples taken from this experimental biocover: For the 1^st, the 0.30-m high sample was compacted with a degree of (water) saturation, Sr = 40% (air-filled porosity = 28.6%). The maximum oxidation rate was 75 g CH₄/m²/d. For the 2^nd, the 0.30-m high sample was placed with Sr = 63% and the maximum oxidation rate was 50 g CH₄/m²/d. For the 3^rd test, a 0.45-m high sample was placed with a Sr = 45% and the maximum oxidation rate attained 141 g CH₄/m²/d. The oxidation rates obtained in the field (with a 0.30-m high substrate) were in the vicinity of 45 g CH₄/m²/d. The rates obtained from column tests were higher than in the field mainly because column samples were not submitted to the elements (precipitation, changes in temperature, exposure to the sun, etc.) but mainly variations in degree of saturation. These results show that laboratory tests can reproduce field conditions, but to a certain extent.