| 1. |
- Hrad, M., et al.
(författare)
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Determination of methane emissions from biogas plants, using different quantification methods
- 2022
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier B.V.. - 0168-1923 .- 1873-2240. ; 326
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Tidskriftsartikel (refereegranskat)abstract
- Reliable and comparable quantification methods are needed for assessing the effectiveness of the biogas production and utilisation process in mitigating methane (CH4) emissions as well as improving the database for emission inventories. The objective of this study was to compare and validate CH4 emissions quantified at two agricultural biogas plants, for up to three days, using diverse on-site (two teams) and off-site methods (three teams), including differential absorption lidar (DIAL), tracer gas dispersion (TDM) and inverse dispersion modelling (IDM). For plant 1, with a constant combined heat and power (CHP) load, the average emission factor varied from 0.3% CH4 (on-site approaches) to 1.2% CH4 (off-site approaches). On-site approaches underestimated overall emissions due to many small (unquantified) CH4 leakages. All methods observed comparable average emission factors for plant 2, ranging between 1.9 and 2.2% CH4. In this case, the majority of emissions emanated from just a few sources. However, correcting the significant influence of the varying CHP load during the measurement campaign revealed significant differences between TDM and IDM (DIAL did not participate). It was demonstrated that TDM and IDM could recover the emission rate from a known point source (controlled release of CH4 via a small diffuser) within an accuracy of 93 ± 15% (TDM) and 92 ± 17% (IDM) under favourable and similar conditions.
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| 2. |
- Monster, J. G., et al.
(författare)
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Quantifying methane emission from fugitive sources by combining tracer release and downwind measurements - A sensitivity analysis based on multiple field surveys
- 2014
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 34:8, s. 1416-1428
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Tidskriftsartikel (refereegranskat)abstract
- Using a dual species methane/acetylene instrument based on cavity ring down spectroscopy (CRDS), the dynamic plume tracer dispersion method for quantifying the emission rate of methane was successfully tested in four measurement campaigns: (1) controlled methane and trace gas release with different trace gas configurations, (2) landfill with unknown emission source locations, (3) landfill with closely located emission sources, and (4) comparing with an Fourier transform infrared spectroscopy (FTIR) instrument using multiple trace gasses for source separation. The new real-time, high precision instrument can measure methane plumes more than 1.2 km away from small sources (about 5 kg h(-1)) in urban areas with a measurement frequency allowing plume crossing at normal driving speed. The method can be used for quantification of total methane emissions from diffuse area sources down to 1 kg per hour and can be used to quantify individual sources with the right choice of wind direction and road distance. The placement of the trace gas is important for obtaining correct quantification and uncertainty of up to 36% can be incurred when the trace gas is not co-located with the methane source. Measurements made at greater distances are less sensitive to errors in trace gas placement and model calculations showed an uncertainty of less than 5% in both urban and open-country for placing the trace gas 100 m from the source, when measurements were done more than 3 km away. Using the ratio of the integrated plume concentrations of tracer gas and methane gives the most reliable results for measurements at various distances to the source, compared to the ratio of the highest concentration in the plume, the direct concentration ratio and using a Gaussian plume model. Under suitable weather and road conditions, the CRDS system can quantify the emission from different sources located close to each other using only one kind of trace gas due to the high time resolution, while the FTIR system can measure multiple trace gasses but with a lower time resolution.
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| 3. |
- Andersen, J. K., et al.
(författare)
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Quantification of Greenhouse Gas Emissions from Windrow Composting of Garden Waste
- 2010
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Ingår i: Journal of Environmental Quality. - : Wiley. - 0047-2425. ; 39:2, s. 713-724
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Tidskriftsartikel (refereegranskat)abstract
- Microbial degradation of organic wastes entails the production of various gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and carbon monoxide (CO). Some of these gases are classified as greenhouse gases (GHGs), thus contributing to climate change. A study was performed to evaluate three methods for quantifying GHG emissions from central composting of garden waste. Two small-scale methods were used at a windrow composting facility: a static flux chamber method and a funnel method. Mass balance calculations based on measurements of the C content in the in- and out-going material showed that 91 to 94% of the C could not be accounted for using the small-scale methods, thereby indicating that these methods significantly underestimate GHG emissions. A dynamic plume method (total emission method) employing Fourier Transform Infra Red (FTIR) absorption spectroscopy was found to give a more accurate estimate of the GHG emissions, with CO2 emissions measured to be 127 +/- 15% of the degraded C. Additionally, with this method, 2.7 +/- 0.6% and 0.34 +/- 0.16% of the degraded C was determined to be emitted as CH4 and CO. In this study, the dynamic plume method was a more effective tool for accounting for C losses and, therefore, we believe that the method is Suitable for measuring GHG emissions from composting facilities. The total emissions were found to be 2.4 +/- 0.5 kg CH4-C Mg-1 wet waste (ww) and 0.06 +/- 0.03 kg N2O-N Mg-1 ww from a facility treating 15,540 Mg of garden waste yr(-1), or 111 +/- 30 kg CO2-equivalents Mg-1 ww.
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| 4. |
- Bai, XN, et al.
(författare)
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Characterization of Clinical Escherichia coli Strains Producing a Novel Shiga Toxin 2 Subtype in Sweden and Denmark
- 2021
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Ingår i: Microorganisms. - : MDPI AG. - 2076-2607. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Shiga toxin (Stx) is the key virulence factor in the Shiga Toxin-Producing Escherichia coli (STEC), which can cause diarrhea and hemorrhagic colitis with potential life-threatening complications. There are two major types of Stx: Stx1 and Stx2. Several Stx1/Stx2 subtypes have been identified in E. coli, varying in sequences, toxicity and host specificity. Here, we report a novel Stx2 subtype (designated Stx2m) from three clinical E. coli strains isolated from diarrheal patients and asymptomatic carriers in Sweden and Denmark. The Stx2m toxin was functional and exhibited cytotoxicity in vitro. The two Swedish Stx2m-producing strains belonged to the same serotype O148:H39 and Multilocus Sequencing Typing (MLST) Sequence Type (ST) 5825, while the Danish strain belonged to the O96:H19 serotype and ST99 type. Whole-genome sequencing (WGS) data analysis revealed that the three Stx2m-producing strains harbored additional virulence genes and the macrolide resistance gene mdf (A). Our findings expand the pool of Stx2 subtypes and highlight the clinical significance of emerging STEC variants. Given the clinical relevance of the Stx2m-producing strains, we propose to include Stx2m in epidemiological surveillance of STEC infections and clinical diagnosis.
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| 5. |
- Bai, XN, et al.
(författare)
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Molecular Characterization and Comparative Genomics of Clinical Hybrid Shiga Toxin-Producing and Enterotoxigenic Escherichia coli (STEC/ETEC) Strains in Sweden
- 2019
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1, s. 5619-
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid E. coli pathotypes are representing emerging public health threats with enhanced virulence from different pathotypes. Hybrids of Shiga toxin-producing and enterotoxigenic E. coli (STEC/ETEC) have been reported to be associated with diarrheal disease and hemolytic uremic syndrome (HUS) in humans. Here, we identified and characterized four clinical STEC/ETEC hybrids from diarrheal patients with or without fever or abdominal pain and healthy contact in Sweden. Rare stx2 subtypes were present in STEC/ETEC hybrids. Stx2 production was detectable in stx2a and stx2e containing strains. Different copies of ETEC virulence marker, sta gene, were found in two hybrids. Three sta subtypes, namely, sta1, sta4 and sta5 were designated, with sta4 being predominant. The hybrids represented diverse and rare serotypes (O15:H16, O187:H28, O100:H30, and O136:H12). Genome-wide phylogeny revealed that these hybrids exhibited close relatedness with certain ETEC, STEC/ETEC hybrid and commensal E. coli strains, implying the potential acquisition of Stx-phages or/and ETEC virulence genes in the emergence of STEC/ETEC hybrids. Given the emergence and public health significance of hybrid pathotypes, a broader range of virulence markers should be considered in the E. coli pathotypes diagnostics, and targeted follow up of cases is suggested to better understand the hybrid infection.
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| 6. |
- Dos Reis Vechi, Natalia, 1992, et al.
(författare)
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Quantification of methane emissions from cattle farms, using the tracer gas dispersion method
- 2022
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809. ; 330
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Tidskriftsartikel (refereegranskat)abstract
- In Denmark, agriculture is the largest source of anthropogenic methane emissions (81%), mainly from cattle (dairy and beef) farms. Whole-farm methane emissions were quantified at nine Danish cattle farms, using the tracer gas dispersion method. Five to six measurement campaigns were carried out at each farm, covering a full year. Of the nine cattle farms, seven were home to dairy cows and two to beef cattle. The farms represented typical breeds, housing and management systems used in Denmark. Whole-farm methane emission rates ranged from 0.7 to 28 kg h−1, with the highest measurements seen at locations with the highest number of animals. Emissions tended to be higher from August to October, due to elevated temperatures and high amounts of stored manure during this period of the year. The average emission factor (EF) for dairy cow farms was 26 ± 8.5 g Livestock Unit (LU)−1 h−1, whereas it was 16 ± 4.1 LU−1 h−1 for beef cattle farms, i.e. 38% lower for the latter. The use of deep litter house management explained some of the differences found in the EFs for dairy cows. Methane emission rates estimated using IPCC models and national guidelines tended, on average for all farms and measurements, to be underestimated by 35% in comparison with the measured methane emissions, for all models and farms. The results suggest that future improvements to inventory models should focus on enteric methane emissions from beef cattle and manure methane emissions for both dairy cows and beef cattle, especially from deep litter management.
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| 7. |
- Karpman, D, et al.
(författare)
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The role of lipopolysaccharide and Shiga-like toxin in a mouse model of Escherichia coli O157:H7 infection
- 1997
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Ingår i: Journal of Infectious Diseases. - : Oxford University Press (OUP). - 0022-1899 .- 1537-6613. ; 175:3, s. 20-611
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Tidskriftsartikel (refereegranskat)abstract
- The role of lipopolysaccharide (LPS) and Shiga-like toxin (SLT) in the pathogenesis of hemolytic uremic syndrome (HUS) was studied in a mouse model. Mice inoculated intragastrically with Escherichia coli O157:H7 developed gastrointestinal, neurologic, and systemic symptoms, necrotic foci in the colon, glomerular and tubular histopathology, and fragmented erythrocytes. LPS-responder (C3H/HeN) mice developed a combination of neurologic and systemic symptoms, whereas LPS-nonresponder (C3H/HeJ) mice had a biphasic course of disease, first developing systemic symptoms and later severe neurologic symptoms. Mice inoculated with SLT-II-positive strains developed severe neurotoxic symptoms and a higher frequency of systemic symptoms and glomerular pathology compared with SLT-II-negative strains. Anti-SLT-II antibodies protected against these symptoms and pathology. These results demonstrate that this model could be used to study aspects of human HUS and that both LPS and SLT are important for disease development.
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| 8. |
- Mellqvist, Johan, 1965, et al.
(författare)
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An uncertainty methodology for solar occultation flux measurements: ammonia emissions from livestock production
- 2024
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Ingår i: Atmospheric Measurement Techniques. - 1867-1381 .- 1867-8548. ; 17:8, s. 2465-2479
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia (NH3/ emissions can negatively affect ecosystems and human health, so they should be monitored and mitigated. This study presents methodology for the estimation of uncertainties in NH3 emissions measurements using the solar occultation flux (SOF) method. The reactive nature of NH3 makes its measurement challenging, but SOF offers a reliable open-path passive method which utilizes solar spectrum data, thereby avoiding gas adsorption within the instrument. To compute NH3 gas fluxes, horizontal and vertical wind speed profiles, as well as plume height estimates and spatially resolved column measurements, are integrated. A unique aspect of this work is the first-time description of plume height estimations derived from ground and column NH3 concentration measurements aimed at uncertainty reduction. Initial validation tests indicated measurement errors between -31 % and C14 % on average, which was slightly larger than the estimated expanded uncertainty ranging from ± 12 % to ± 17 %. Application of the methodology to assess emission rates from farms of various sizes showed uncertainties between ± 21 % and ± 37 %, generally influenced by systematic wind uncertainties and random errors. The method demonstrates the capacity to measure NH3 emissions from both small (~ 0.5 1 kg h-1/ and large (~ 100 kg h-1/ sources in high-density farming areas. Generally, the SOF method provided an expanded uncertainty below 30 % in measuring NH3 emissions from livestock production, which could be further improved by adhering to best application practices. This paper s findings offer the potential for broader applications, such as measuring NH3 fluxes from fertilized fields and in the oil and gas sector. However, these applications would require further research to adapt and refine the methodologies for these specific contexts.
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| 9. |
- Scheutz, C., et al.
(författare)
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Gas production, composition and emission at a modern disposal site receiving waste with a low-organic content
- 2011
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 31:5, s. 946-955
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Tidskriftsartikel (refereegranskat)abstract
- AV Miljo is a modern waste disposal site receiving non-combustible waste with a low-organic content. The objective of the current project was to determine the gas generation, composition, emission, and oxidation in top covers on selected waste cells as well as the total methane (CH(4)) emission from the disposal site. The investigations focused particularly on three waste disposal cells containing shredder waste (cell 1.5.1), mixed industrial waste (cell 2.2.2), and mixed combustible waste (cell 1.3). Laboratory waste incubation experiments as well as gas modeling showed that significant gas generation was occurring in all three cells. Field analysis showed that the gas generated in the cell with mixed combustible waste consisted of mainly CH(4) (70%) and carbon dioxide (CO(2)) (29%) whereas the gas generated within the shredder waste, primarily consisted of CH(4) (27%) and nitrogen (N(2)) (71%), containing no CO(2). The results indicated that the gas composition in the shredder waste was governed by chemical reactions as well as microbial reactions. CH(4) mass balances from three individual waste cells showed that a significant part (between 15% and 67%) of the CH(4) generated in cell 1.3 and 2.2.2 was emitted through leachate collection wells, as a result of the relatively impermeable covers in place at these two cells preventing vertical migration of the gas. At cell 1.5.1, which is un-covered, the CH(4) emission through the leachate system was low due to the high gas permeability of the shredder waste. Instead the gas was emitted through the waste resulting in some hotspot observations on the shredder surface with higher emission rates. The remaining gas that was not emitted through surfaces or the leachate collection system could potentially be oxidized as the measured oxidation capacity exceeded the potential emission rate. The whole CH(4) emission from the disposal site was found to be 820 +/- 202 kg CH(4) d(-1). The total emission rate through the leachate collection system at AV Miljo was found to be 211 kg CH(4) d(-1). This showed that approximately 1/4 of the emitted gas was emitted through the leachate collections system making the leachate collection system an important source controlling the overall gas migration from the site. The emission pathway for the remaining part of the gas was more uncertain, but emission from open cells where waste is being disposed of or being excavated for incineration, or from horizontal leachate drainage pipes placed in permeable gravel layers in the bottom of empty cells was likely. (C) 2010 Published by Elsevier Ltd.
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| 10. |
- Scheutz, C., et al.
(författare)
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Mitigation of methane emission from an old unlined landfill in Klintholm, Denmark using a passive biocover system
- 2014
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 34:7, s. 1179-1190
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Tidskriftsartikel (refereegranskat)abstract
- Methane generated at landfills contributes to global warming and can be mitigated by biocover systems relying on microbial methane oxidation. As part of a closure plan for an old unlined landfill without any gas management measures, an innovative biocover system was established. The system was designed based on a conceptual model of the gas emission patterns established through an initial baseline study. The study included construction of gas collection trenches along the slopes of the landfill where the majority of the methane emissions occurred. Local compost materials were tested as to their usefulness as bioactive methane oxidizing material and a suitable compost mixture was selected. Whole site methane emission quantifications based on combined tracer release and downwind measurements in combination with several local experimental activities (gas composition within biocover layers, flux chamber based emission measurements and logging of compost temperatures) proved that the biocover system had an average mitigation efficiency of approximately 80%. The study showed that the system also had a high efficiency during winter periods with temperatures below freezing. An economic analysis indicated that the mitigation costs of the biocover system were competitive to other existing greenhouse gas mitigation options. (C) 2014 Elsevier Ltd. All rights reserved.
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