LFG emission measurements in cold climatic conditions: seasonal variations and methane emissions mitigation

Landfill gas (LFG) emissions were measured at three landfills in Northern Sweden and Northern Finland. Several strategies for measuring gas emissions in winter conditions (i.e., a snow-covered surface and frozen ground) were tested. Static chambers appeared to be the most suitable measurement technique. The study results showed that winter measurements should be done directly at the soil surface and that any snow cover should be removed beforehand. A seasonal variation of the emissions was observed. Methane emissions were measured during late winter at the three sites and during late summer at two of the same three sites. Monitoring performed during the different seasons yields a better estimation of the annual LFG emissions. Variations in methane oxidation are likely sources of any differences as low temperature and low soil water content both reduce methane oxidation activity. At low emission rates, the main methane emission may occur during wintertime because of the mitigation effect landfill cover has on methane oxidation during summertime. A reduced methane oxidation activity was observed during the late summer at two of the sites. A combination of summer dryness and heat from methane oxidation is believed to have dried the soil, which then caused a subsequent decrease in methane oxidation. To use landfill covers for the management of methane emissions in cold climates, special consideration must be given to the moisture and extreme low temperature factors.