Efficiency of methane biotransformation of soil and soil-like biofilters in Moscow
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Methane biofiltration is based on gas transformation to carbon dioxide and water by methanotrophic microorganisms. Biofilter performance has been thoroughly investigated under climatic conditions of Western Europe, but not those of Russia. Therefore, this study was conducted to analyze methane biotransformation performance of soil and soil-like biofilters in Moscow.
Materials and methods
Biofilters were designed as three-layer systems (0.2 × 0.2 × 0.5 m) where methane (2.5 vol%) was injected daily. This system operated for 9 months. Five biofilters with different working layers have been investigated: a natural humic horizon of albeluvisol (AB); two soil-like types of media containing peat (PB) or compost (CB) as organic matter; and two soil-like types of media containing the reclamation additives vermiculite (CVB) and clayite (CCB). Methane and carbon dioxide were measured in hermetically covered biofilters immediately and 24 h after methane injection. These gases were collected through a six-tube system incorporated into the biofilters and analyzed by gas chromatography.
Results and discussion
The maximum methane biotransformation occurred in summer, while there was slightly less in autumn and much less in winter. The highest values of 99.7, 97.0, and 91.5 % were observed in AB, followed by 97.8, 92.4, and 72.8 % in CB and 52.6, 43.2, and 23.8 % in PB during summer, autumn, and winter, respectively. Methane biotransformation rates were correlated with methanotroph pools in biofilter media. Summer carbon dioxide levels were lowest in AB (0.7 %) and highest in CB (2.6 %) due to difference in organic composition and its mineralization rates. Emission levels were highest in AB (0.2 %) driven by the maximum porosity of this media providing gas transport to the atmosphere; CVB had the lowest carbon dioxide emission (0.02 %) due to incorporation of sorptive additive. Carbon dioxide generation generally stopped during winter, while increasing acidity was observed in summer and autumn because of the formation of carbonic acid, and redox potential increased significantly in winter due to carbon dioxide elimination.
Under Moscow’s climatic conditions, biofilters can perform efficiently during summer and autumn, but methane biotransformation is much lower during winter. CVB showed the greatest potential for use under these conditions owing to its high methane biotransformation and low carbon dioxide emissions.
KeywordsBiofilters Biotransformation Carbon dioxide Methane Methanotrophs Soil
This study was supported by the Russian Foundation for Basic Research, project number 12-04-00435 and 14-05-31284.
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