Methane oxidation in a landfill biowindow under wide seasonally fluctuating climatic conditions

In the current study, a pilot biowindow was constructed in a closed cell of a Canadian Landfill, undergoing high seasonal fluctuations in the temperature from −30 in winter to 35 in summer. The biowindow was filled with biosolids compost amended with yard waste and leaf compost with the ratio of 4:1 as the substrate layer. Two years of monitoring of methane (CH 4 ) oxidation in the biowindow led to remarkable expected observations including a thick, solid winter frost cover affecting gas exchange in winter and temperatures above 45 ℃ in the biowindow in late summer. A high influx compared to the reported values was observed into the biowindow with an average value of 1137 g.m −2 .d −1 , consisting of 64% of CH 4 and 36% of carbon dioxide (CO 2 ) in the landfill gas. The variations in the temperature and moisture content (MC) of the compost layer in addition to the influx fluctuations affected CH 4 oxidation efficiency; however, a high average CH 4 oxidation rate of 237 g.m −2 .d −1 was obtained, with CH 4 being mostly oxidized at top layers. The laboratory batch experiments verified that thermophilic methane-oxidizing bacteria (MOB) were active throughout the study period and oxidized CH 4 with a higher rate than mesophilic MOB. The methanotrophic potential of the compost mixture showed an average value of 282 µmol.g −1 .d −1 in the entire period of the study which is in the range of the highest reported maximum CH 4 oxidation rates. The adopted compost mixture was suitable for CH 4 oxidation if the MC was above 30%. The significance of MC variations on CH 4 oxidation rate depended on the temperature range within the biowindow. At temperatures below 2 ℃, between 29 and 31℃, and above 45 ℃, MC was not a controlling factor for mesophilic CH 4 oxidation. Graphical abstract