To better understand how much methane escapes from the U.S. natural gas supply chain – and from where – EDF spearheaded an extensive research series. It revealed that methane emissions are 60 percent higher than the government estimate.
For this effort, we brought together more than 140 research and industry experts [PDF] from 40 institutions and 50 companies.
The series is divided into 16 distinct projects, whose insights – published from 2013 to 2018 – will help inform policies and opportunities to minimize methane emissions.
1. Natural gas production site emissions
This study led by the University of Texas at Austin measured methane emissions at natural gas production sites – including some of the first measurements ever collected from hydraulically fractured wells.
Diverse methods were used to directly measure methane emissions at well pads operated by nine cooperating U.S. natural gas companies. The study found that methane emissions from equipment leaks and pneumatic devices were larger than previously thought.
The study also found that techniques to reduce emissions from well completions are effective at capturing 99 percent of the methane that was previously vented to the atmosphere, providing a data-based example of EPA regulations working.
- Measurements of methane emissions at natural gas production sites in the United States (Proceedings of the National Academy of Sciences, October 2013)
- Possible malfunction in widely used methane sampler deserves attention but poses limited implications for supply chain emission estimates (Elementa, December 2016)
2. Production site emissions – additional data
This study expands on results from the first University of Texas study by collecting additional data from two important emission sources associated with natural gas production:
- Liquid unloadings, when producing wells are cleared of water and other liquids inhibiting the flow of gas.
- Pneumatic controllers used to regulate routine functions at well sites.
UT coordinated with 10 natural gas companies on this effort. The study found that emissions from the two sources were responsible for a significant portion of methane emissions from the production sector.
- Methane emissions from process equipment at natural gas production sites in the United States: Pneumatic controllers (Environmental Science and Technology, December 2014)
- Methane emissions from process equipment at natural gas production sites in the United States: Liquid Unloadings (Environmental Science and Technology, December 2014)
3. Production data analysis to investigate trends
EPA’s Office of Research and Development has collected fence line data on methane emissions at well production sites over several years. EPA, Houston Advanced Research Center and EDF worked together to analyze the data further to investigate trends in production emissions.
The report includes measurements from 210 production sites in the Barnett Shale and Eagle Ford regions of Texas, Colorado’s Denver-Julesburg Basin and the Upper Green River Basin gas fields surrounding Pinedale, Wyoming, from 2010 to 2013.
A statistical analysis of this data suggests unpredictable events, such as malfunctions and maintenance, have a strong influence on emission rates.
Assessment of methane emissions from oil and gas production pads using mobile measurements (Environmental Science and Technology, November 2014)
4. Emissions during gathering and processing
Colorado State University’s Engines and Energy Conversion Laboratory led an effort to quantify national methane emissions associated with the natural gas industry’s gathering infrastructure and gas processing facilities.
Researchers worked with six industry companies and used tracer gas releases to quantify methane emissions from this sector. The study found methane leakage from gathering activities is eight times larger than official estimates.
Researchers with the study suggest leak detection and repair policies can be effective at minimizing emissions from these sources.
- Measurements of methane emissions from natural gas gathering facilities and processing plants: Measurements results (Environmental Science and Technology, February 2015)
- Measurements of methane emissions from natural gas gathering facilities and processing plants: Measurement methods (Atmospheric Measurement Techniques, May 2015)
- Methane emissions from United States natural gas gathering and processing (Environmental Science and Technology, August 2015)
5. Emissions during transport and storage
Researchers with Colorado State University, Carnegie Mellon University and Aerodyne Research – in cooperation with seven industry partners – estimated the amount of methane lost during long-distance transportation and storage of natural gas.
The initial measurements paper used downwind tracer gas methods paired with direct on-site measurements to report variable emissions data from site to site.
The paper confirms compressors and equipment leaks are two primary sources for the sector’s methane emissions. Researchers also developed a model to combine their measurements with data from EPA’s Greenhouse Gas Reporting Program to derive a national emissions estimate for this industry segment.
- Methane emissions from natural gas compressor stations in the transmission and storage sector: Measurements and comparisons with the EPA greenhouse gas reporting program protocol (Environmental Science and Technology, February 2015)
- Methane emissions from the natural gas transmission and storage system in the United States (Environmental Science and Technology, July 2015)
Local distribution studies
6. Emissions during delivery: Multiple cities
Washington State University’s Laboratory for Atmospheric Research led a nationwide field study to better characterize and understand methane emissions associated with the delivery of natural gas.
Researchers quantified methane emissions from facilities and pipes operated by 13 utilities in various regions. The data will be used to estimate emissions from distribution systems nationally.
The study shows that methane emissions from local natural gas distribution systems are significant, especially in regions such as the Northeast, where distribution infrastructure is older, but that progress is being made in reducing emissions from these systems, mainly through regulation and investment by utilities.
Direct measurements show decreasing methane emissions from natural gas local distribution systems in the United States (Environmental Science and Technology, March 2015)
7. Emissions in an urban area: Boston
Scientists with Harvard, Boston and Duke universities, along with Aerodyne Research and Atmospheric and Environmental Research, developed an innovative tower-based quantitative technique for use in the urban environment.
The study found Boston’s methane emissions are more than two times higher than inventory data suggests, with a yearly average loss rate between 2.1 and 3.3 percent.
Methane emissions from natural gas infrastructure and use in the urban region of Boston, Massachusetts (Proceedings in the National Academy of Sciences, January 2015)
8. Emissions in an urban area: Indianapolis
To gain further regional insights of urban methane emissions, Washington State University coordinated with the National Institute of Standards and Technology, Aerodyne, GHD, Purdue and Pennsylvania State universities to measure methane emissions in Indianapolis, as part of a broader NIST project.
The study found that natural gas end-use sources – such as gas meters, furnaces, boilers and hot water heaters – as well as landfills, are responsible for a large portion of urban methane emissions.
Direct and indirect measurements and modeling of methane emissions in Indianapolis, Indiana (Environmental Science and Technology, August 2016)
9. Mapping methane with mobile sensors
Using mobile methane sensors, EDF partnered with Google to map methane emissions from pipelines under city streets.
Led by researchers at Colorado State University, this method quantifies methane leaks from local distribution systems that utilities could use to identify and prioritize repair or replacement of leaky pipelines, not otherwise addressed as an immediate public safety risk. Learn more at edf.org/methanemaps.
Rapid, vehicle-based identification of location and magnitude of urban natural gas pipeline leaks (Environmental Science and Technology, March 2017)
10. Emissions from the Denver-Julesburg Basin
Researchers with the National Oceanic Atmospheric Administration and University of Colorado at Boulder measured methane emissions from Colorado’s most active oil and gas field using data gathered by aircrafts and compared the differences in atmospheric concentrations of hydrocarbons upwind and downwind of production areas.
The study estimated methane emissions that were three times higher than estimates derived from EPA data. The study also found that levels of smog-forming volatile organic compounds were twice as high as EPA estimates, and benzene levels were seven times higher than previously estimated.
A new look at methane and non-methane hydrocarbon emissions from oil and natural gas operations in the Colorado Denver-Julesburg Basin (Journal of Geophysical Research: Atmospheres, May 2014)
11. Emissions from the Barnett Shale in Texas
EDF convened 12 diverse research teams in October 2013 to measure methane emissions in the Barnett Shale in Texas. This campaign used a variety of aircraft, vehicle and ground-based measurements to quantify methane emitted across the natural gas supply chain.
A preliminary study estimated regional methane emissions to be 50 percent higher than emission estimates in EPA’s Greenhouse Gas Inventory, with subsequent research estimating emissions could be as much as 90 percent higher.
Mobile laboratory observations of methane emissions in the Barnett Shale region (Environmental Science and Technology, March 2015)
Measuring emissions from oil and natural gas well pads using the mobile flux plane technique (Environmental Science and Technology, March 2015)
Near-field characterization of methane emission variability from a compressor station using a model aircraft (Environmental Science and Technology, May 2015)
Using multi-scale measurements to improve methane emission estimates from oil and gas operations in the Barnett Shale region, Texas (Environmental Science and Technology, July 2015)
Constructing a spatially resolved methane emission inventory for the Barnett Shale region (Environmental Science and Technology, July 2015)
Toward a functional definition of methane super-emitters: Application to natural gas production sites (Environmental Science and Technology, July 2015)
Airborne ethane observations in the Barnett Shale: Quantification of ethane flux and attribution of methane emissions (Environmental Science and Technology, July 2015)
Methane emissions from leak and loss audits of natural gas compressor stations and storage facilities (Environmental Science and Technology, July 2015)
Aircraft-based measurements of point source methane emissions in the Barnett Shale basin (Environmental Science and Technology, July 2015)
Characterizing fugitive methane emissions in the Barnett Shale area using a mobile laboratory (Environmental Science and Technology, July 2015)
Integrating source apportionment tracers into a bottom-up inventory of methane emissions in the Barnett Shale hydraulic fracturing region (Environmental Science and Technology, July 2015)
Reconciling divergent estimates of oil and gas methane emissions (Proceedings of the National Academy of Sciences, December 2015)
Super-emitters in natural gas infrastructure are caused by abnormal process conditions (Nature Communications, January 2017)
12. Barnett Shale emssions: Flyover study
As part of a broader project (No. 11), scientists with NOAA, UC-Boulder’s Cooperative Institute for Research in Environmental Sciences and the University of Michigan are measuring atmospheric concentrations of hydrocarbons in order to quantify and allocate regional methane emissions in an active oil and gas basin that includes infrastructure.
Publication:Aircraft-based estimate of total methane emissions from the Barnett Shale region (Environmental Science and Technology, July 2015)
13. Emissions from natural gas-fueled vehicles
West Virginia University’s Center for Alternative Fuels, Engines and Emissions, in cooperation with 10 companies and research organizations, led a study to directly measure methane emissions from the operation of natural gas-fueled medium- and heavy-duty vehicles, as well as compressed natural gas and liquefied natural gas refueling and maintenance facilities.
Researchers found that the largest sources of vehicular-related methane emissions came from tailpipes (30 percent) and crank cases (39 percent).
Emissions from fueling stations were relatively low, accounting for about 12 percent of transport segment emissions.
Publication:Pump-to-wheels methane emissions from the heavy-duty transportation sector (Environmental Science and Technology, December 2016)
14. Pilot projects
Three initial projects helped build the foundation for some of this research. University of Texas-Arlington collected methane data using mobile methane-sensing technology that helped inform the first UT study (No.1), as well as the Coordinated Campaign (No. 11 and No. 12) and the methane mapping.
Harvard, Duke and Boston University researchers experimented with tower-based sensing systems for making methane emissions estimates in an urban environment. This work led to the larger Boston study (No. 7).
University of Colorado-Boulder scientists conducted research to identify elevated levels of methane and hydrogen sulfide that provided insights for subsequent overflight work (No. 10 and No. 11).
15. Prevalence of high-emitting sources
Researchers used infrared technology to conduct an aerial survey of over 8,000 well pads in seven geologic basins across the country to characterize the prevalence of “super emitters” – the sources responsible for a disproportionate amount of methane and VOC pollution in the oil and gas production sector.
The study concludes super emitters are highly widespread and unpredictable but easily identified through better and more frequent monitoring.
Aerial surveys of elevated hydrocarbon emissions from oil and gas production sites (Environmental Science and Technology, April 2016)
Emissions of coalbed and natural gas methane from abandoned oil and gas wells in the United States (American Geophysical Union – Geophysical Research Letters, February 2016)
16. Synthesis of the five-year project
EDF engaged stakeholders from across the projects to develop an integrated understanding of what was learned. This collaboration found that U.S. oil and gas methane emissions are 60 percent higher than official estimates suggest, emphasizing the critical need to tackle this pollution.
Synthesis of recent ground-level methane emission measurements from the U.S. natural gas supply chain (Science Direct, April 2017)