| Summary: | It has been shown that CH 4 emitted to the atmosphere from landfills can be oxidized by methanotrophic bacteria in landfill top covers. Therefore, it should be feasible to develop a mitigation strategy incorporating a combination of engineered and natural methanotrophic controls, by means of a designed landfill cover that would promote growth of methane oxidizing bacteria, while performing its other purposes. Such an approach might provide a complementary strategy for the control of CH 4 emissions, particularly at older sites where flaring or energy recovery is not economically feasible. In the case of modern landfills, a passive methane oxidation barrier (BOPM) would permit to reduce emissions of greenhouse gas (GHG) and after the period of active gas collection, i.e. from the moment when it is not longer economically viable to extract biogas. This prompted an ongoing multidisciplinary project that jointly considers geotechnical, hydraulic, physical, chemical, environmental, climatic and microbiological aspects in assessing the efficiency of landfill cover materials that would act as PMOB. More specifically, the present report deals with two aspects of this project, i.e. characterization and laboratory testing in columns (controlled oxidation) and, thereafter, the realization of field tests. The column tests were carried out in order to determine the oxidation rate of a sand-compost mixture used on the experimental cells in the field. The oxidation rates varied between 1284 and 4555 g CH4 /m 2 /d. Three PMOBs were built on the existing final cover of the St-Nicephore landfill, Quebec, Canada. Within the PMOBs, temperature and water content values were measured at 4 different reference depths at 4 different profiles en each cell and the data was recorded by dataloggers. In addition, meteorological data were continuously recorded by a weather station. The main goals of this field experiment are to evaluate CH 4 abatement. If in the beginning of the monitoring period there was considerable CH 4 abatement, as time passed, heavy rainfalls caused the oxidation front to move upwards. As expected, the degree of saturation was sensitive to variations in rainfall values equal or greater to 15 mm/d. The atmospheric pressure underwent some important variations; for example, -3.5 kPa during one day and +2.5 kPa in two days. Such variations influence the entry of O 2 , which affects oxidation rates and biogas migration upwards.
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