Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/17282
Methane oxidizing biosystems have received wide recognition in the past years as a cost effective and important means to reduce emissions from landfills. However, there is no documentation of the oxidation capacity of Icelandic landfill covers to date and there is limited information on microbial methane oxidation in boreal climates. The present study was carried out to qualitatively assess the oxidation capacity of the current top cover of one of the cells of the Fíflholt landfill, located in West Iceland, using the gas profile method (CO2/CH4 ratio). The landfill has no gas recovery system and the cover is composed of 15-25 cm crushed wood overlain by about 1 m of gravelly sand with 7% organic matter content. Sampling probes were installed at two locations on cell 2 at different depths (5 to 120 cm) and point gas concentration measurements were carried out during the autumn and the winter of 2012-2013. It was observed that atmospheric air penetrated deep into the cover and oxidation activity was observed in the gas profiles. The oxidation zone was situated mainly below 40 cm from the surface and went as deep as about 1 m below surface, i.e. to the base of the cover. Oxidation efficiencies ranged from 0 to 99%, reaching the maximal value between 30 and 60 cm depth, with mean values 59% and 77% for the two sampling locations and for the study period. It must be highlighted that relatively high oxidation efficiencies were obtained during the winter, indicating that methane oxidation can take place throughout the year. The study also suggests that the 10% default oxidation factor proposed by the IPCC model may underestimate the actual oxidation capacity of the cover at the Fíflholt landfill, although a more thorough and continuous measurement campaign is needed to confirm this hypothesis.