Methane is an important greenhouse gas that has contributed ∼25% of the radiative forcing experienced to date. Despite methane’s short atmospheric lifetime (~10 years), the global methane mole fraction has increased three times faster than carbon dioxide since 1750. Methane emission mitigation is an effective way to reduce the short-term rate of warming, and is essential to IPCC pathways that limit warming below 2 C. In contrast to carbon dioxide, anthropogenic methane emissions originate from a large variety and number of diffuse point sources that are mostly independent of combustion processes. As a result, systematic, international atmospheric measurements are needed to inform emission inventories and mitigation strategies.
This session will highlight field research and satellite studies that focus on methane emissions from human activities (e.g., oil and gas production, coal mining, fire, rice production, ruminants, landfills and waste). Particular emphasis is on atmospheric observations at different spatio-temporal scales with the aim to (1) reduce the uncertainty in the measured magnitude of emissions, (2) identify source-specific emission patterns and mitigation opportunities, and (3) inform government, industry, and other stakeholders on mitigation pathways.
vPICO presentations: Fri, 30 Apr
Methane (CH4), the second most important greenhouse gas in terms of radiative forcing, is on the rise; but there are extensive opportunities for mitigation with existing technologies. Anthropogenic emissions account for around 60% of the global methane source, and the recent atmospheric methane growth rate puts us on a trajectory comparable to the most extreme future methane scenarios in the sixth Coupled Model Intercomparison Project (CMIP6).
We use a new methane emissions-driven configuration of the UK Earth System Model (UKESM1) to explore the role of anthropogenic methane in the earth system. The full methane cycle is represented, including surface deposition, chemistry and interactive wetland emissions. As a baseline scenario we used Shared Socioeconomic Pathway 3-7.0 (SSP3-7.0) – the highest methane emissions scenario in CMIP6. In an idealised experiment, all anthropogenic methane emissions were instantaneously stopped from 2015 onwards in a coupled atmosphere-ocean simulation running from 2015-2050, to make a net-zero anthropogenic methane emissions scenario.
Within a decade, significant changes can be seen in atmospheric composition and climate, compared to SSP3-7.0. The atmospheric methane burden declines to below pre-industrial levels within 12 years, and by the late 2030s reaches a constant level around 44% below that of the present day (2015). The tropospheric ozone burden and surface mean ozone concentrations decreased by 12% and 15% respectively by 2050 – key in terms of limiting global warming as well as improving air quality and human health.
By 2050 the net-zero anthropogenic methane scenario results in a global mean surface temperature (GMST) 1˚C lower than the baseline, a significant value in the context of climate goals such as the Paris Agreement. Through decomposition of the radiation budget, the change in climate can be directly attributed to the reduction in methane and indirectly to the resulting changes in ozone, clouds and ozone precursors such as CO. In addition, the changes in climate result in impacts on the interactive wetland emissions via changes in temperature and wetland extent, highlighting the coupled nature of methane in the earth system.
Cessation of anthropogenic methane emissions has profound impacts on near-term warming and on tropospheric ozone, but ultimately cannot single-handedly achieve the necessary reductions for meeting Paris goals.
How to cite: Staniaszek, Z., Griffiths, P. T., Folberth, G. A., O'Connor, F. M., and Archibald, A. T.: Climate and composition impacts of a net-zero anthropogenic methane future using an emissions-driven chemistry-climate model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5740, https://doi.org/10.5194/egusphere-egu21-5740, 2021.
MEMO2 was a 4-years European Training Network with more than 20 collaborators from 7 countries. The project contributed significantly to the targets of the EU with a focus on methane (CH4). CH4 emissions are a major contributor to Europe’s global warming impact, and the official inventories of emissions and estimates derived from direct atmospheric measurement show significant discrepancies. However, effective emission reduction can only be achieved if sources are properly quantified, and mitigation efforts are verified. MEMO2 contributed to advanced combinations of measurement and modelling which are needed to achieve such quantification.
With respect to the recently released EU methane strategy and the implementation of independent verification of emissions by atmospheric measurements, we will present some examples of relevant results from MEMO2 up to now:
Urban CH4 emissions: We can now detect and quantify CH4 leaks in cities at the street-level with mobile nigh precision analysers. Similar studies have been carried out in >10 EU cities and in collaboration with interested network operators those measurements are ready to be rolled out at larger scale.
Oil and gas production: We carried out a large study in the oil and gas production region in Romania (ROMEO), with aircraft, drones and vehicles. The final results are close to publication and help to improve the emission verification.
Coal mining: In collaboration with CoMet, another science project, we quantified the CH4 emissions from the Upper Silesian coal mining area. The collaboration and its results contribute to the development of an independent and objective emission monitoring system
Modelling: Micro-scale plume modelling is significantly improved. Those models e.g. help to simulate a measurement day as we had during our field campaign in Romania and improve sampling and measurement strategies.
How to cite: Walter, S. and Röckmann, T. and the the MEMO2 Team: MEMO2: MEthane goes MObile – MEasurements and MOdelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3244, https://doi.org/10.5194/egusphere-egu21-3244, 2021.
Romania has been a pioneer country in oil and gas (O&G) exploration in Europe and is the largest producer of O&G in Central and Eastern Europe. However, many installations are old and production levels are decreasing. The ROMEO measurement campaign was carried out in Romania to evaluate methane emissions form onshore O&G operations in Romania in 2019 (ROMEO, 2019). In this program, Technical University of Denmark (DTU) and TNO used mobile-van-based measurements in combination with tracer release to quantify emissions. A total set of 200 oil and gas wells, and facilities were evaluated and emissions were quantified. Methane emission rates ranged largely between about 0.02 and 38 g s-1, following a “heavy-tailed” lognormal distribution. A small number of sites (5%) were responsible for 55% of the total emission. Decreasing emissions only from the few high-emitters would effectively decrease methane emissions from the investigated area. This shows the value of site-specific evaluation from the ground. In this presentation, the mobile measurement equipped vans will be shown and methodological issues will be addressed. Also the results in terms of the emission distribution will be presented. The outcome of this study can help the Romanian O&G companies to set priorities in leak repair, which can then lead to a quick win in emission reduction.
ROMEO, 2019. ROMEO - ROmanian Methane Emissions from Oil & gas. URL http://romeo-memo2.wikidot.com/ (last accessed 13.01.21).
How to cite: Velzeboer, I., Delre, A., Hensen, A., van den Bulk, P., and Scheutz, C.: Evaluation of oil and gas methane emissions in Romania using mobile measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8935, https://doi.org/10.5194/egusphere-egu21-8935, 2021.
Atmospheric methane (CH4) is an extremely potent greenhouse gas, with ever-increasing global emissions expected to have a significant influence on the Earth’s climate. The Oil and Gas sector is considered to be a significant source of CH4 to the atmosphere, estimated to make up approximately 22% of global emissions. Offshore facility emissions are poorly ground-truthed, with their quantification being heavily dependent on “bottom-up” scaling of inventory data. It is therefore important to devise reliable methods for locating these emissions and to pinpoint their sources, as this will aid emission quantification and validation against reported data.
As part of the United Nations Climate and Clean Air Coalition (UN CCAC) project, this study aims to characterise CH4 emissions from oil and gas infrastructure in the Norwegian Sea. The campaign comprised surveys of selected operational oil and gas platforms in this region and included targeted observations of CH4. These surveys were conducted by the Facility of Airborne Atmospheric Measurements (FAAM) and Scientific Aviation Mooney research aircrafts in July and August 2019, with a total 14 flights. Fluxes are derived using a mass balance approach and aircraft sampling. The Lagrangian particle dispersion model “FLEXPART” is used to aid the attribution of the observed CH4 emissions to the platform(s). We will present results for derived fluxes and uncertainties for individual facilities in the Norwegian Sea. These fluxes will be compared with emissions estimates from platform operators, as well as a global, gridded emission inventory.
How to cite: Foulds, A. and the North Sea Methane Team: Quantification of methane emissions from offshore oil & gas platforms in the Norwegian Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9536, https://doi.org/10.5194/egusphere-egu21-9536, 2021.
Atmospheric methane (CH4) concentrations have more than doubled since the beginning of the industrial era, making methane the second most important anthropogenic greenhouse gas after carbon dioxide (CO2). Fossil fuel extraction is one of the major anthropogenic methane sources as it is estimated to account for 22 % of global CH4 emissions. However, studies indicate that inventories underestimate emissions arising from the oil and gas industry.
In two airborne field campaigns carried out in spring 2018 and 2019 offshore gas facilities in the Southern North Sea were probed. A total of nine research flights were conducted to characterize platform emissions. The Twin Otter research aircraft, operated by the British Antarctic Survey, was equipped with a high-precision 10 Hz analyzer (Picarro) to continuously measure CH4 and CO2. In order to identify fossil fuel emissions ethane (C2H6) was simultaneously measured with a 1 Hz TILDAS instrument (Aerodyne Research, Inc). On offshore oil and gas platforms methane is emitted by leakage, venting or flaring. To catch the methane plume, stacked transects were flown downwind of single platforms or platform complexes.
Methane fluxes were calculated for six British and four Dutch facilities using the mass balance method. Correlations with C2H6 and CO2 were found with the latter indicating partly combusted methane from flaring. Uncertainties of fluxes arise mainly due to uncertainty of the wind measurement and the plume height. The calculated fluxes were compared to emissions reported to inventories (UK National Atmospheric Emissions Inventory (NAEI), UK Environmental and Emissions Monitoring System database (EEMS), Scarpelli inventory (2016)) and individually reported emissions from Dutch operators.
How to cite: Pühl, M., Roiger, A., Fiehn, A., Schwietzke, S., Allen, G., Foulds, A., Lee, J., France, J. L., Lachlan-Cope, T., Warwick, N., and Pisso, I.: Aircraft mass balance estimate of methane emissions from offshore gas facilities in the Southern North Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15428, https://doi.org/10.5194/egusphere-egu21-15428, 2021.
Methane is a potent greenhouse gas and the primary component of natural gas (NG). There has been a significant increase in the production and use of NG in recent years, partly due to the perceived environmental benefits associated with NG in comparison to other fossil fuels. One of the growing elements in the global market for NG is the role of liquefied natural gas (LNG). LNG provides a means for global trade in NG, with gas being liquified close to production sites, shipped internationally as LNG and imported and fed into national gas infrastructure at regassification plants. LNG use has increased in recent years and in 2019 approximately 482.4 Gm3 was traded, making the sixth consecutive year of market growth.
As part of the 2015 United Nations Climate Change Conference, COP 21, the Environmental Defence Fund along with industrial partners pledged to better quantify the oil and gas industry’s contribution to global methane emissions across the value chain. From this a series of peer-reviewed scientific studies to quantify methane emissions in the oil and gas sector were commissioned in collaboration with the Climate and Clean Air Coalition, the Oil and Gas Climate Initiative and European Commission. As part of this wider study, the National Physical Laboratory (NPL) is undertaking a programme of measurements to quantify the methane emissions from key stages of the LNG supply chain using a variety of measurement techniques, including the Differential Absorption Lidar (DIAL) facility designed and operated by NPL.
DIAL is a powerful technique that can be used to track and quantify plumes emitted from complex emission sources including LNG plants. By using Lidar, the DIAL technique can make remote range-resolved single-ended measurements of the actual distribution of target gases in the atmosphere, with no disruption to normal site operational activities. It provides 3D mapping of emission concentrations and quantification of emission rates for a wide range of target gases, including methane.
Within this study an initial selection and prioritisation of sites was made based on a number of criteria. The measurement approach has been to quantify the emissions from the sites over a period of weeks, determining emissions from the key functional elements of the sites. Data has therefore been obtained for total site emissions and related to the different processes on the sites. Throughput data from the sites has also been collected to enable comparisons between the emissions.
This talk will describe the objectives and scope of the project and the methodology used to characterise the sites by their functional elements. The benefits in comparing data with this level of granularity will be discussed. The DIAL measurements were conducted using a methodology which is the basis for a draft standard method for fugitive monitoring currently being developed by CEN in Europe. The method, performance characteristics and validation data will be described. A summary of the current status of the field measurements and a discussion on the results obtained so far will be given. Future work and expected outcomes will be discussed.
How to cite: Innocenti, F., Robinson, R., Gardiner, T., Howes, N., and Yarrow, N.: Update on a global study measuring methane emissions from Liquid Natural Gas facilities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5730, https://doi.org/10.5194/egusphere-egu21-5730, 2021.
Goal of the CCAC project is to observe urban emission of natural gas over Canada and different countries in Europe. Our team was responsible for the Silesia and Sub-Carpathia regions in southern Poland. In this presentation we will focus on the methane emission measurements from gas pipelines, storages, gas wells as well as gathering and processing facilities, which was realized by our team in years 2018-2020.
South eastern Poland is rather rural part of the country with rich history of oil and gas industry going back to the XVI-th century. Currently Carpathians and Carpathian Foredeep regions gas industry produces 1.35 BILLIONS of m3 
The measurements have been carried out since summer 2016 mainly with Micro-Portable Greenhouse Gas Analyzer ‘Los Gatos Research, MGGA-918’ mounted on board of a car. We also had capability to deploy analyser in difficult terrain with its own power supply. During our measurements our team visited over 300 gas wells. We found that over half of these sites show elevated methane concentrations which can be attributed to either gas well itself or soil fractures around site. Transects paths were designed to follow pipelines. This allowed us to monitor possible leaks from the natural gas infrastructure. However there are numerous possible sources in close proximity of pipelines. We will discuss detection methods and variability study for dozens of transects. As of the 2017 only 9 gathering and processing facilities report release which states the emission of 1.8*106 m3 CH4 per year. One of the focus points of our project was to estimate how uncertain were methane emission from O&G in Poland which at current phase concludes methane emission of 7.5-40 kt CH4/year
During the presentation we will outline challenges in carrying out measurements with GPM, OTM 33a methods that were performed alongside large-area screening. We are developing oversized flow chamber method. Mobile structure is built in the shape of a dome. It has the radius of 3 meters which gives the chamber volume of 49 m3.
This work was funded under the Climate and Clean Air Coalition (CCAC) Oil and Gas Methane Science Studies.
PSG, „Bilans zasobów złóż kopalin w Polsce wg stanu na 31 XII 2019 r,” PIG-PIB, Warsaw, 2020.
How to cite: Jagoda, P., Nęcki, J., Bartyzel, J., Korbeń, P., Kud, M., Florczyk, G., and Król, S.: The extent of methane emission associated with the natural gas industry in southeastern Poland., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12214, https://doi.org/10.5194/egusphere-egu21-12214, 2021.
On October 14, 2020 the European Commission adopted the EU methane strategy. Measurement-based reporting of methane emissions will be crucial and may become legally binding. A variety of different methods are in use to quantify methane emissions from natural gas distribution networks, some attempting to quantify the pipeline leak under the ground, others attempting to quantify the emissions to the atmosphere. Comparisons between these methods are essential, as each method has its own advantages and limitations. In August and September 2020, we conducted an extensive campaign to compare three different methods, the mobile survey method, the tracer release method, and the suction techniques, to quantify emission rates of leaks from the natural gas distribution network in Hamburg, Germany. The mobile measurement technique employed two different cavity ringdown analyzers to identify and quantify methane, ethane and carbon dioxide using a moving vehicle. The tracer release technique measured methane and the tracer gas acetylene also with fast laser methods during driving or stationary deployment in a vehicle at an identified leak location. The suction method deployed soil sondes around an identified leak and measured methane in a stream of air pumped out of the soil until an equilibrium was reached. In total, we targeted 20 locations that had been identified by mobile measurements or by the routine leak detection of the local gas utility, GasNetz Hamburg. For numerous locations we detected several emission outlets from e.g., cavities, cracks or drains and we used measurements of the ethane to methane ratio to identify possible mixture of fossil and microbial sources. We will compare the different quantification methods, including their suitability for routine application and precision and accuracy in emission quantification.
How to cite: Maazallahi, H., Delre, A., Buth, L., Fredenslund, A. M., Nagler, I., Scheutz, C., Schwietzke, S., Denier van der Gon, H., and Röckmann, T.: Detection and quantification method intercomparison of methane emission from natural gas distribution network leaks in Hamburg, Germany, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16140, https://doi.org/10.5194/egusphere-egu21-16140, 2021.
The Permian Basin is the largest and fastest growing oil and gas (O&G) producing region in the United States. Methane (CH4), a powerful greenhouse gas, is emitted from both routine and abnormal or avoidable operating conditions in the Permian Basin, including O&G production, distribution, and processing. The time scales over which these emissions persist is uncertain, and this uncertainty can lead to large discrepancies in bottom-up emission accounting. Here, we conducted an extensive airborne campaign across the majority (55,000 km2) of the Permian Basin with imaging spectrometers to quantify individual CH4 point sources at the facility scale. We revisited each source multiple times and found that CH4 sources exhibited 26% persistence on average. Persistence-averaged CH4 emissions follow a heavy-tailed distribution, with 20% of facilities constituting 60% of the total point source budget. We quantified the total CH4 flux in the region (point + area sources) through an inverse analysis with satellite observations, and find that point sources make up 50% of the regional CH4 budget. Sector attribution of plumes shows that 50% of detected emissions result from O&G production, 38% from gathering, and 12% from processing plants. Imaging spectroscopy allows for identification of flares, and we find that 12% of CH4 plume emissions were associated with either active or inactive flares, and often emitting above 1000 kg CH4 h-1, even under active flaring. These results show that regular plume-scale monitoring in heterogeneous O&G basins is necessary to understand the high intermittency of operations and resulting emissions.
How to cite: Cusworth, D., Duren, R., Thorpe, A., Dennison, P., Downey, N., Green, R., Olson-Duvall, W., Chapman, J., Eastwood, M., Asner, G., Heckler, J., and Miller, C.: Transient methane emissions in the Permian Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13824, https://doi.org/10.5194/egusphere-egu21-13824, 2021.
The Permian Basin is known for its extensive oil and gas production, which has increased rapidly in recent years becoming the largest producing basin in the United States. It is also responsible for almost half of the methane emissions from all oil and gas producing regions in the country. Given the urgent need to reduce greenhouse gas emissions, it is crucial to identify and characterize the point sources of emissions. To this end, we have combined three new high-resolution hyperspectral sensors data onboard the GF-5, ZY1 and PRIMA satellites to create the first regional study to identify methane sources and measure the emitted quantities from each source. With data collected over several days in 2019 and 2020, we have identified a total of 37 point source emissions with flux rates >500kg/h, that is, a high concentration of extreme emission point sources that account for nearly 40% of the Permian annual emissions. Also, we have found that new infrastructure (post-2018) is responsible for almost 60% of the detected emissions, in many cases (21% of the cases) due to inefficient use of flaring of the gas that they cannot store. With this study, we demonstrate that hyperspectral satellite data are a powerful tool for the detection and quantification of strong methane point emissions.
How to cite: Irakulis-Loitxate, I., Guanter, L., Liu, Y.-N., Varon, D. J., Maasakkers, J. D., Zhang, Y., Chulakadabba, A., Wofsy, S. C., Thorpe, A. K., Duren, R. M., Frankenberg, C., Lyon, D., Cusworth, D. H., Zhang, Y., Segl, K., Gorroño, J., Sánchez-García, E., Sulprizio, M. P., Aben, I., and Jacob, D. J.: Satellite-based characterization of methane point sources in the Permian Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15877, https://doi.org/10.5194/egusphere-egu21-15877, 2021.
In the context of the Paris Agreement goal of limiting global warming to below 2 degrees Celsius, the Representative Concentration Pathways (RCP) 2.6 of the Intergovernmental Panel on Climate Change (IPCC) have framed greenhouse gas emission scenarios emphasizing a sharp reduction in methane (CH4) emissions with the current increasing trend. Recent studies have shown that satellite observations of atmospheric methane can be used to detect and quantify localized methane sources on a facility-level for the oil and gas industry. We use satellite observations from TROPOMI to understand the high and persistent methane signals from ventilation shafts in the coal mining industry. Even the bottom-up and top-down global estimates infer coal mine methane responsible for ~12% of the anthropogenic methane emissions. TROPOMI onboard Sentinel-5P has a ground pixel resolution of 5 × 7 km2 at nadir, which allows detection of large local to point sources. With its daily global coverage, we identify high methane emission sources over coal mine regions in Australia during 2018 and 2019 and quantify methane emissions using the fast data-driven cross-sectional flux method. Our initial results show that TROPOMI estimates are higher than bottom-up global emission inventories. We will present emission estimates using satellite-based quantification for super-emitter coal mines and evaluate its implication on national greenhouse gas reporting.
How to cite: Sadavarte, P., Pandey, S., Maasakkers, J. D., Lorente, A., Borsdorff, T., Denier van der Gon, H., Houweling, S., and Aben, I.: Quantifying Methane Emissions from Super-emitter Coal Mines using TROPOMI Observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15693, https://doi.org/10.5194/egusphere-egu21-15693, 2021.
Methane (CH4) emissions from coal production are one of the main sources of anthropogenic CH4 in the atmosphere. Poland is the second largest hard coal producer in the European Union with the Polish area of the Upper Silesian Coal Basin (USCB) as a part of it. Emission estimates for CH4 from USCB for individual coal mine ventilation shafts range between 0.03kt CH4/yr and 25.9kt CH4/yr, amounting to a basin total of roughly 465kt CH4/yr (E-PRTR database, 2014). During CoMet (Carbon Dioxide and Methane Mission 2018) four ground-based, portable FTIR (Fourier transform infrared) spectrometers EM27/SUN were deployed in the USCB. We arranged these instruments in fixed locations in the North, East, South, and West of the USCB in approx. 50km distance to the center of the basin. This set-up ensures both, upwind and downwind measurements of CH4 for the prevailing wind directions. Subtracting upwind from downwind XCH4 observations gives the net methane enhancement of the region in between two selected instruments. These enhancements are also modeled with the Lagrangian particle dispersion model Flexpart. The model is driven by WRF wind simulations calculated in a nested domain using data assimilation of 3D wind-lidar data measured at three locations in the area of interest. The residuals between modeled and measured enhancements are minimized with a Phillips-Tikhonov regularized, non-negative least squares approach using the E-PRTR inventory data as a-priori information. The regularization parameters are graphically chosen via L-curve determination. Simulation uncertainty is expressed through an ensemble of different model runs, each with altered, basic meteorological parameters. The model generally matches the E-PRTR inventory data within it's error range for a small number (6 to 10) of coal mine ventilation shafts, whereas it suggests higher emission rates than the E-PRTR for more involved point sources (>30).
How to cite: Luther, A., Kleinschek, R., Kostinek, J., Stanisavljevic, M., Dandocsi, A., Forstmaier, A., Defratyka, S., Scheidweiler, L., Wildmann, N., Dubravica, D., Hase, F., Frey, M., Chen, J., Dietrich, F., Knote, C., Nęcki, J., Roiger, A., and Butz, A.: Estimating coal mine methane emissions using ground-based FTIR spectrometry, WRF driven Lagrangian dispersion modelling, and a regularized inversion approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12751, https://doi.org/10.5194/egusphere-egu21-12751, 2021.
Methane (CH4) is a potent greenhouse gas; therefore, accurate measurement of its sources is important for climate research. Because of the diversity of methane sources, identifying and apportioning different sources is essential. We demonstrate our ability characterize a specific source using top-down atmospheric observations downwind of a coal mine vent shaft, a large natural gas source, in San Juan, NM. To facilitate a field campaign in December of 2020, a mobile platform was developed to make simultaneous in situ observations of methane and ethane (C2H6) with an Aeris mid-IR spectrometer and wind velocities with a Trisonica mini 3-D anemometer. Total column methane was also measured during the campaign using an EM27/SUN mobile solar Fourier transform spectrometer (FTS) and compared with column methane and ethane measured in March of 2013 using higher resolution FTS instruments at a TCCON station near the site1. Our in situ data shows a unique and stable C2H6:CH4 ratio of 1-2% in the vent plume that agrees well with the 1.5% ratio measured by the TCCON FTS instruments in 2013, demonstrating that consistent attribution can be made using both in situ and remote methods. Furthermore, we infer the mass flux of methane and ethane from the vent shaft using a simple plume dispersion model and multiple measurements around the vent shaft. This direct source inversion is compared to results from a trained neural network code we have developed for source location and quantification (ALFaLDS)2. Our results demonstrate how multiscale measurements, inverse modeling, and machine learning can be used to better attribute and constrain methane emissions.
1 Lindenmaier, R. et al.: Multiscale observations of CO2, 13CO2, and pollutants at Four Corners for emission verification and attribution, Proc. Natl. Acad. Sci., 111 (23), 8386-8391, https://doi.org/10.1073/pnas.1321883111, 2014.
2 Travis, B., Dubey, M. and Sauer J.: Neural networks to locate and quantify fugitive natural gas leaks for a MIR detection system, Atmos. Environ: X, 8, (2020) 100092, https://doi.org/10.1016/j.aeaoa.2020.100092, 2020.
How to cite: Meyer, A., Lindenmaier, R., Travis, B., Heerah, S., and Dubey, M.: Multiscale Natural Gas Emissions Observations of the San Juan, NM Coal Mine: Inversion Using Plume and Neural Network Models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12827, https://doi.org/10.5194/egusphere-egu21-12827, 2021.
Emissions from fossil fuels are one of the primary sources of atmospheric methane (CH4) growth. However, estimates of anthropogenic CH4 emissions still show large uncertainties on global and regional scales. Differences in CH4 isotopic source signatures δ13C and δD can help to constrain different source contributions (e.g. fossil, thermogenic, or biogenic).
The Upper Silesian Coal Basin (USCB) represents one of the largest European CH4 emission source regions, with more than 500 Gg CH4 yr-1 released by more than 50 coal mine ventilation shafts. During the CoMet (Carbon Dioxide and Methane Mission) campaign in June 2018 methane observations were conducted from a variety of platforms including aircraft and cars. Beside the continuous sampling of atmospheric methane concentration, numerous air samples were taken from inside the ventilation shafts, around the ventilation shafts (1‑2 km distance) and aboard the DLR Cessna Caravan aircraft and analyzed in the laboratory for the isotopic composition of CH4.
The ground-based samples allowed determining the source signatures of individual ventilation shafts. These signatures displayed a considerable range between different shafts and also varied from day to day. The airborne samples contained a mixture of methane emissions from several mines and thus enabled accurately determining the signature of the entire region. The mean isotopic signature of methane emissions over the USCB derived from the aircraft samples was -51.9 ± 0.5 ‰ for δ13C and -233 ± 6 ‰ for δD. This is in between the range of other microbial and thermogenic coal reservoirs, but more depleted in δD than previous USCB studies reported based on samples taken within the mines. Signatures of methane enhancements sampled upwind of the mines and in the free troposphere clearly showed the presence of methane of biogenic origin (e.g. wetlands, waste, ruminants).
Furthermore, we simulated the methane isotopologues using the on-line three-times nested global regional chemistry climate model MECO(n). We implemented a submodel extension, which includes the kinetic fractionation and uses the isotopic source signatures determined by the ground-based observations. We compare the regional simulations to flask samples taken during CoMet.
How to cite: Fiehn, A., Kostinek, J., Eckl, M., Galkowski, M., Gerbig, C., Röckmann, T., Menoud, M., Maazallahi, H., Schmidt, M., Korben, P., Necki, J., Stanisavljevic, M., Swolkien, J., Nickl, A.-L., Winterstein, F., Mertens, M., Jöckel, P., Fix, A., and Roiger, A.: Isotopic characterization of coal mine methane in the Upper Silesian Coal Basin, Poland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6056, https://doi.org/10.5194/egusphere-egu21-6056, 2021.
The climate change impact of methane is significant and the recent increase in its atmospheric concentrations raises great concerns. Across Canada, methane emissions are unevenly distributed with a large part attributed to the Western Canadian Sedimentary Basin (WCSB), which is the fourth largest reserve of fossil fuels in the world. The WCSB extends from northeastern British Columbia to southwestern Manitoba, encompassing Alberta and southern Saskatchewan. The extraction of hydrocarbons mostly takes place in the provinces of Alberta and Saskatchewan and is a large source of methane.
According to recent international agreements, the Government of Canada has committed to reducing methane emissions by 40 to 45% by 2025 based on 2012 levels. However, a recent study using atmospheric measurements of methane concentrations in the region showed that methane emissions from the oil and gas sector might be nearly twice that reported in Canada’s National Inventory (Chan et al., 2020). More investigations are required to better understand the discrepancy between these two estimates.
In this study, we use atmospheric observations of δ13C measured successively at three locations across the WCSB between 2016 and 2020 to help identify the influence of different types of methane sources across the provinces of Alberta and Saskatchewan. We compare our atmospheric measurements with compilations and isotope contour maps of fugitive methane from energy facilities across the basin. Combining these measurements with trajectories computed with the HYSPLIT model developed by NOAA, we show a gradient in the methane isotopic signature across Alberta: methane being more depleted in southwestern Saskatchewan than northwestern Alberta. We also used the HYSPLIT5-STILT dispersion model to derive footprints during our measurements and estimate methane contributions of these two provinces using an optimization based on the isotopic measurements.
Chan et al. 2020:
How to cite: Vogel, F., Ars, S., Muehlenbachs, K., Gonzalez Arismendi, G., and Worthy, D.: Using atmospheric in-situ measurements of 13CH4 to investigate methane emissions in Western Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10349, https://doi.org/10.5194/egusphere-egu21-10349, 2021.
Methane (CH4) emissions from human activities are a threat to the resilience of our current climate, and to the adherence of the Paris Agreement goals. The stable isotopic composition of methane (δ13C and δ2H) allows to distinguish between the different CH4 origins. A significant part of the European CH4 emissions, 10 % in 2016, comes from the Upper Silesian Coal Basin (USCB).
Measurements of CH4 mole fraction (χ(CH4)), δ13C and δ2H in CH4 in ambient air were performed continuously during 6 months in 2018 and 2019 at Krakow, Poland. In addition, CH4 samples were collected during parallel mobile campaigns, from multiple CH4 sources in the footprint area of continuous measurements. The resulting isotopic signatures from natural gas leaks, coal mine fugitive emissions, landfill and sewage, and ruminant emissions were statistically different. The use of δ2H in CH4 is crucial to distinguish the fossil fuel emissions in the case of Krakow, because their relatively depleted δ13C values overlap with the ones of microbial sources. The observed χ(CH4) time series showed a regular daily night-time accumulations, sometimes combined with irregular pollution events during the day. The isotopic signatures of each peak were obtained using the Keeling plot method, and generally fall in the range of thermogenic CH4 formation, with δ13C between -55.3 and -39.4 ‰ V-PDB, and δ2H between -285 and -124 ‰ V-SMOW. They compare well with the signatures measured for gas leaks in Krakow and USCB mines.
The CHIMERE transport model was used to compute the CH4 time series at the study location, based on two emission inventories. The χ(CH4) are generally under-estimated in the model. The isotopic signatures of all pollution events over the entire time periods were extracted from Keeling plots applied on each peaks, for both observed and modelled time series using the EDGAR v5.0 inventory. The results indicate that a higher contribution from fuel combustion sources in the inventory would lead to a better agreement. The isotopic mismatches between model and observations are mainly caused by uncertainties in the assigned isotopic signatures for each source category, and how they are classified in the inventory. These uncertainties are larger for emissions close to the study site, which are more heterogenous than the ones advected from the USCB coal mines. Our isotope approach proves here to be very sensitive in this region, thus helping to improve emission estimates.
How to cite: Menoud, M., van der Veen, C., Necki, J., Stanisavljevic, M., Szenási, B., Pison, I., Bousquet, P., and Röckmann, T.: Isotopic characterisation of methane emissions from Krakow, Poland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10697, https://doi.org/10.5194/egusphere-egu21-10697, 2021.
Atmospheric CH4 mixing ratios resumed their increase in 2007 after a plateau during the period 1999-2006, suggesting a change of mix between sources and/or varying sinks. Exploiting observations within an inverse modeling framework (top-down estimates) is a powerful approach that reconciles observed and simulated CH4 mixing ratios using prior knowledge of CH4 sources and sinks. It is nevertheless challenging to efficiently differentiate co-located emissions from different sectors categories with CH4 observations alone. As a result, understanding CH4 burden changes and attributing these changes to specific source variations are difficult. CH4 source isotopic signatures differ between emission categories (biogenic, thermogenic and pyrogenic), and can therefore be included to disentangle overlapping sources.
However, assimilating 13CH4 observations using inversion methods is challenging, especially with a variational framework. Here, a new 3-D variational inverse modeling framework implemented within the Community Inversion Framework [Berchet et al., 2020] and designed to assimilate 13CH4 and CH3D observations along CH4 observations is presented. This system is capable of optimizing emissions and associated source signatures of multiple emission categories independently at the pixel scale. Multiple tracers are transported by the LMDz 3-D model in order to properly simulate the clumped isotopologues of CH4.
We present very briefly the technical implementation of such multi-constraints in the variational system and show preliminary results of long-term inversions for the period 1998-2018.
Berchet, A., Sollum, E., Thompson, R. L., Pison, I., Thanwerdas, J., Broquet, G., Chevallier, F., Aalto, T., Bergamaschi, P., Brunner, D., Engelen, R., Fortems-Cheiney, A., Gerbig, C., Groot Zwaaftink, C., Haussaire, J.-M., Henne, S., Houweling, S., Karstens, U., Kutsch, W. L., Luijkx, I. T., Monteil, G., Palmer, P. I., van Peet, J. C. A., Peters, W., Peylin, P., Potier, E., Rödenbeck, C., Saunois, M., Scholze, M., Tsuruta, A., and Zhao, Y.: The Community Inversion Framework v1.0: a unified system for atmospheric inversion studies, Geosci. Model Dev. Discuss. [preprint], https://doi.org/10.5194/gmd-2020-407, in review, 2020.
How to cite: Thanwerdas, J., Saunois, M., Berchet, A., Pison, I., and Bousquet, P.: Running a new 3-D variational inversion system to assimilate isotopic observations along with CH4 observations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4077, https://doi.org/10.5194/egusphere-egu21-4077, 2021.
Methane is an important greenhouse gas with a range of anthropogenic sources, including livestock farming and fossil fuel production. It is important that methane emissions can be correctly attributed to their source, to aid climate change policy and emissions mitigation efforts. For source attribution, many ‘top-down’ models of atmospheric methane use spatial maps of sources from emissions inventory data coupled with an atmospheric transport model. However, this can cause difficulties if sources are co-located or if there is uncertainty in the sources’ spatial distributions.
To help with this issue and reduce overall uncertainty in estimates of methane emissions, recent methods have used observations of a secondary trace gas and its correlation with methane to infer methane emissions from a target sector. Most previous work has assumed a fixed emissions ratio between the two gases, which often does not reflect the true range of possible emission ratios. In this work, measurements of atmospheric ethane and its emissions ratio relative to methane are used to infer emissions of methane from fossil fuel sources. Instead of assuming a fixed emission ratio, our method allows for uncertainty in the emission ratio to be statistically propagated through the inverse model and incorporated into the sectoral estimates of methane emissions. We further demonstrate the inaccuracies that can result in an assessment of fossil fuel methane emissions if this uncertainty is not considered.
We present this novel method for modelling sectoral methane emissions with examples from a synthetic data experiment and give results from a case study of UK methane emissions. Methane and ethane observations from a tall tower network across the UK were used with this model to produce monthly estimates of UK fossil fuel methane emissions with improved uncertainty characterisation.
How to cite: Ramsden, A., Ganesan, A., Western, L., Manning, A., Rigby, M., Say, D., Wisher, A., Arnold, T., Rennick, C., Levy, P., Young, D., and O'Doherty, S.: Quantifying methane emissions from fossil fuel sources using a Bayesian inverse model and observations of ethane with an uncertain emissions ratio, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8869, https://doi.org/10.5194/egusphere-egu21-8869, 2021.
The efficient and precise monitoring (detection, localization, and quantification) of fugitive methane (CH4) emissions is essential in preventing and mitigating greenhouse gas (GHG) emissions from oil and gas industrial facilities and landfills. Various strategies of mole fraction sampling within or in the vicinity of the sites and of atmospheric inversions have been developed for such a monitoring. Many studies have ensured the constant improvement of instrumentation, of measurement strategies and atmospheric inversion techniques.
In this context, we participated in two controlled-release experiments at the TOTAL Anomaly Detection Initiatives (TADI) test site (Lacq, France) in October 2018 and 2019, dedicated to evaluate the ability of different local-scale atmospheric measurement and inverse modeling systems to localize and quantify point sources. We also conducted a series of 18 campaigns to regularly quantify methane emissions from the active “Butte-Bellot” landfill (about 35 km south-east of Paris) since 2018. We developed and applied different inversion approaches to process mobile or fixed-point measurements, which, in both cases, rely on a Gaussian dispersion model to simulate the atmospheric plume from the potential source location or mole fraction sensitivity at the measurement time and location to emissions at the potential source locations.
The series of CH4 and carbon dioxide (CO2) controlled releases in TADI covered a wide range of release rates (~0.1 to 200 gCH4/s and 0.2 to 200 gCO2/s) and durations from 4 to 8 minutes (brief) to 25 to 75 minutes (longer). During the corresponding campaigns, we conducted both near-surface mobile and fixed-point (~2-4 m height) in situ atmospheric measurements based on Picarro CRDS, LGR (MGGA and UGGA), and LI-COR (LI-7810) instruments. Both inversions based on mobile measurements and those based on the fixed-point measurements provide estimates with a 20-30% average error for the CH4 and CO2 release rates, whatever the duration of the releases. The use of fixed-point measurements during long releases allow for a more precise localization of sources with an average location error of ~8m.
The analysis of the CH4 mobile measurements at the “Butte-Bellot” landfill reveals the difficulties in exploiting measurements close to such a site with diffuse emissions whose spatial distribution is difficult to characterize, heterogeneous and highly variable in time. The series of estimates of the total CH4 emissions from the site based on remote mobile plume cross-sections, based on atmospheric inversions, are discussed.
This presentation will highlight positive perspectives opened by the proposed inversion approaches and by our results and discuss options for further improvements when processing both types of measurements.
How to cite: Kumar, P., Broquet, G., Caldow, C., Laurent, O., Yver-Kwok, C., Cropley, F., Fontanier, B., Shah, A., Lozano, M., Defratyka, S., Gichuki, S., Lauvaux, T., Rivera, R., Berthe, G., Martin, F., Noirez, S., Duclaux, O., Juery, C., Bouchet, C., and Ciais, P. and the TRACE team: Local-scale atmospheric inversions to monitor CH4 emissions from industrial sites using mobile and/or fixed-point measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12743, https://doi.org/10.5194/egusphere-egu21-12743, 2021.
Biological methane oxidation in landfill cover material can be characterised using stable isotopes. Methane oxidation fraction is calculated from the carbon isotopic signature of emitted CH4, with enhanced microbial consumption of methane in the aerobic portion of the landfill cover indicated by a shift to less depleted isotopic values in the residual methane emitted to air. This study was performed at four southwest England landfill sites. Mobile mole fraction measurement at the four sites was coupled with Flexfoil bag sampling of air for high-precision isotope analysis. Gas well samples collected from the pipeline systems and downwind plume air samples were utilized to estimate methane oxidation rate for whole sites. This work was designed to assess the impact on carbon isotopic signature and oxidation rate as UK landfill practice and waste streams have changed in recent years.
The landfill status such as closed and active, seasonal variation, cap stripping and site closure impact on landfill isotopic signature and oxidation rate were evaluated. The isotopic signature of 13C-CH4 values of emissions varied between -60 and -54‰, with an averaged value of -57 +- 2‰ for methane from closed and active landfill sites. Methane emissions from older, closed landfill sites were typically more enriched in 13C than emissions from active sites. This study found that the isotopic signature of 13C-CH4 of fugitive methane did not show a seasonal trend, and there was no plume observed from a partial cap stripping process to assess changes in 13C-CH4 isotopic signatures of emitted methane. Also, the closure of an active landfill cell caused a significant decrease in mole fraction of measured CH4, which was less depleted 13C in the emitted plume due to a higher oxidation rate. Methane oxidation, estimated from the isotope fractionation, ranged from 3 to 27%, with mean values of 7% and 15% for active and closed landfills, respectively. These results indicate that the oxidation rate is highly site specific.
How to cite: Bakkaloglu, S., Lowry, D., Fisher, R., France, J., and Nisbet, E.: UK landfill methane emissions: Use of mobile plume measurements and carbon isotopic characterisation to reassess oxidation rates for open and closed sites , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8192, https://doi.org/10.5194/egusphere-egu21-8192, 2021.
Methane (CH4) emissions from landfills contribute to global warming, impacting significantly the environment and human health. Landfill CH4 emissions strongly depend on changes in barometric pressure, inducing short-term CH4 emission variation of several orders of magnitude. Estimating the temporal variability of CH4 emitted into the atmosphere could help us reducing the uncertainties of annual emission estimates from landfills. In this study, we focus on the temporal variability of CH4 emissions under the impact of barometric pressure changes.
CH4 emissions of a closed landfill (Skellingsted, Western Zealand, Denmark) were measured with two different methods from December 2019 to June 2020; continuously with the eddy covariance method (EC) and discretely with the dynamic tracer dispersion method (TDM). The EC method allows continuous measurements from a confined surface area, with most likely limited representativeness of the whole landfill site due to the considerable horizontal heterogeneity. The TDM method is able to quantify the emission from the whole site insensitive of the topography with the limited representativeness for the temporal variability.
CH4 emissions to the atmosphere measured by the TDM and fluxes measured by the EC ranged from to 0 to almost 100 kg h-1 and from 0 to 10 μmol m-2 s-1, respectively. The CH4 fluxes measured continuously using the EC method were highly correlated with the emissions from the periodic measurements using the TDM and fluctuated according to the pressure tendency. Under decreasing barometric pressure the highest CH4 emissions where observed, while increasing barometric pressure suppressed them almost to 0.
Our results demonstrate the value of implementing two different complementary measurement techniques in parallel that will help to quantify total annual CH4 emission from a landfill. EC method provides continuous measurements describing accurately the temporal variation of emissions, while TDM method is able to quantify emissions from the whole site.
How to cite: Kissas, K., Ibrom, A., Kjeldsen, P., and Scheutz, C.: Temporal variability of methane emissions from a closed landfill at Denmark, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12518, https://doi.org/10.5194/egusphere-egu21-12518, 2021.
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