Methane budgets (production = emissions + oxidation + recovery) were estimated for six landfill sites in Sweden. Methane oxidation was measured in downwind plumes with a stable isotope technique (Chanton, J. P., et al., Environ. Sci. Technol. 1999, 33, 3755-3760.) Positions in plumes for isotope sampling as well as methane emissions were determined with an optical instrument (Fourier Transform InfraRed) in combination with N2O as tracer gas (Galle, B., et al., Environ. Sci. Technol. 2001, 35, 21-25.) Two landfills had been closed for years prior to the measurements, while four were active. Measurements at comparable soil temperatures showed that the two closed landfills had a significantly higher fraction of oxidized methane (38-42% of emission) relative to the four active landfills (4.6-15% of emission). These results highlight the importance of installing and maintaining effective landfill covers and also indicate that substantial amounts of methane escape from active landfills. Based on these results we recommend that the IPCC default values for methane oxidation in managed landfills could be set to 10% for active sites and 20% for closed sites. Gas recovery was found to be highly variable at the different sites, with values from 14% up to 65% of total methane production. The variance can be attributed to different waste management practices. © 2007 American Chemical Society.

Biogas is upgraded using an absorption with water-wash technique by 11 of a total of 14 upgrading plants in Sweden. However, problems with microbial growth on the pall rings in the absorption column, and in one case in the desorption column, have a negative impact on the upgrading of raw gas to vehicle gas. Five of the nine biogas plants studied here have experienced problems with microbial growth. The objectives of this study were to identify such microbial growth and to determine possible factors for its control, in order to provide recommendations for process management. A questionnaire was sent out and visits were made to the upgrading plants to collect information about the upgrading process. Phospholipid fatty acid (PLFA) analysis was performed to determine microbial biomass and community structure in samples from four upgrading plants. In samples from two of the plants, methane-oxidizing bacteria (type I methanotrophs) were indicated, while samples from one of the other plants showed biomarkers indicating actinomycetes. Factors affecting development of microbial growth were found to be water quality and the pH and temperature of the process water. Plants that used wastewater in the upgrading process experienced far more problems than those using clean water of drinking quality. © 2007 Humana Press Inc.

Biological oxidation of CH4 is an important constraint on the emission of this gas from areas, such as landfills to the atmosphere. We studied the effect of temperature on methanotrophic bacteria in three different landfill cover soils, incubated in the laboratory. In samples of a young cover, consisting of wood chips and sewage sludge, the phospholipid fatty acids (PLFAs), regarded as biomarkers for type I methanotrophs (16:1?5t, 16:1?6c, 16:1?8c), primarily increased at low temperatures (5-10°C). On the other hand, the PLFA marker for type II methanotrophs (18:1?8c) was highly elevated only at 20°C. These results suggest that temperature can determine the selection of methanotroph populations. © 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

Methanethiol and carbon disulphide were investigated for their ability to inhibit methane oxidation in two landfill cover soils. Methanethiol was found to be a competitive inhibitor, and at concentrations occurring in landfills, both these VSCs (volatile sulfur compounds) had inhibitory effects on the methane oxidation rates. Analysis of the phospholipid fatty acid contents in the soils indicated that type I, methanotrophs were more affected than type II. These effects of VSCs on methane oxidation are likely to have implications both for the establishment and the selectivity of a methane oxidizing microflora in landfills.

Methane is an important climate gas contributing significantly to global warming. A large part of the anthropogenic emissions of methane comes from landfills. Due to the biogenic origin of these emissions and the inhomogeneous characteristics of landfills and their soil cover, these emissions show large spatial variation. Thus, development of reliable and cost-effective methods for measurements of these emissions is an important task and a challenge to the scientific community. Traditionally, field chamber methods have been used but also different area integrating methods based on downwind plume measurements. These measurements have been supported by meteorological data either directly from local measurements or by controlled release of tracer gas from the landfill providing the dispersion characteristics of the plume. in this paper we describe a method, the Time Correlation Tracer method, combining controlled tracer gas release from the landfill with time-resolved concentration measurements downwind the landfill using FTIR absorption spectroscopy. The method has been tested and used on measurements at a landfill in southern Sweden over the past 1.5 years. The method has proven to be a usable method for measurements of total methane emission from landfills, and under favorable meteorological conditions we estimate an achievable accuracy of 15-30%. The real time analysis capability of the FTIR makes it possible to judge the success of the measurement already on site and to decide whether more measurements are necessary. The measurement strategy is relatively simple and straightforward, and one person can make a measurement from a medium sized landfill (1-4 ha) within a few days to a week depending on the meteorological situation.

The release of methane (CH4) from landfills to the atmosphere and the oxidation of CH( in the cover soils were quantified with static chambers and a C-13-isotope technique on two landfills in Sweden. One of the landfills had been closed and covered 17 years before this investigation while the other was recently covered. On bath landfills, the tops of the landfills were compared with the sloping parts in the summer and winter. Emitted CH4, captured in chambers, was significantly enriched in C-13 during summer compared with winter (P < 0.0001), and was enriched relative to anaerobic-zone methane, The difference between emitted and anaerobic zone delta C-13-CH4 was used to estimate soil methane oxidation. In summer, these differences ranged from 9 to 26 parts per thousand, and CA(4) oxidation was estimated to be between 41 and 50% of the produced CHI in the new landfill, and between 60 and 94% in the old landfill. In winter, when soil temperature was below 0 degreesC, no difference in delta C-13 was observed between emitted and anaerobic-zone CH4 suggesting that there was no soil oxidation. The temperature effect shown in this experiment suggests that there may be both seasonal and latitudinal differences in the importance of landfill CH4 oxidation. Finally the isotopic fractionation factor to) varied from 1.023 to 1.038 and was temperature dependent, increasing at colder temperatures. Methanotrophic bacteria appeared to have high growth efficiencies and the majority of the methane consumed in incubations did not result in immediate CO2 production.

We compared methane oxidation activity in laboratory incubations of samples from a podzolic soil profile to the microbial community structure of the soil, determined as the content and composition of phospholipid fatty acids (PLFAs). The abundances of two fatty acids considered unique for methanotrophs (and the abundances of all other quantified PLFAs) were very weakly related to methane oxidation. This is in contrast to the situation in environments with much higher methane supply, indicating that these fatty acids should not be used as biomarkers for methanotrophs in upland forest soils. (C) 2000 Elsevier Science Ltd.