skip to main content


Title: Comparison of methane emission estimates from multiple measurement techniques at natural gas production pads

This study presents the results of a campaign that estimated methane emissions at 268 gas production facilities in the Fayetteville shale gas play using onsite measurements (261 facilities) and two downwind methods - the dual tracer flux ratio method (Tracer Facility Estimate - TFE, 17 facilities) and the EPA Other Test Method 33a (OTM33A Facility Estimate - OFE, 50 facilities). A study onsite estimate (SOE) for each facility was developed by combining direct measurements and simulation of unmeasured emission sources, using operator activity data and emission data from literature. The SOE spans 0-403 kg/h and simulated methane emissions from liquid unloadings account for 88% of total emissions estimated by the SOE, with 76% (95% CI [51%-92%]) contributed by liquid unloading at two facilities. TFE and SOE show overlapping 95% CI between individual estimates at 15 of 16 (94%) facilities where the measurements were paired, while OFE and SOE show overlapping 95% CI between individual estimates at 28 of 43 (65%) facilities. However, variance-weighted least-squares (VWLS) regressions performed on sets of paired estimates indicate statistically significant differences between methods. The SOE represents a lower bound of emissions at facilities where onsite direct measurements of continuously emitting sources are the primary contributormore » to the SOE, a sub-selection of facilities which minimizes expected inter-method differences for intermittent pneumatic controllers and the impact of episodically-emitting unloadings. At 9 such facilities, VWLS indicates that TFE estimates systematically higher emissions than SOE (TFE-to-SOE ratio = 1.6, 95% CI [1.2 to 2.1]). At 20 such facilities, VWLS indicates that OFE estimates systematically lower emissions than SOE (OFE-to-SOE ratio of 0.41 [0.26 to 0.90]). Given that SOE at these facilities is a lower limit on emissions, these results indicate that OFE is likely a less accurate method than SOE or TFE for this type of facility.« less
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ; ORCiD logo [3] ;  [4] ;  [5] ;  [5] ;  [5] ;  [5] ;  [5]
  1. Colorado State Univ., Fort Collins, CO (United States). Energy Inst. and Mechanical Engineering
  2. Aerodyne Research, Inc., Billerica, MA (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  4. National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States). Earth System Research Lab.; Univ. of Colorado, Boulder, CO (United States). Cooperative Inst. for Research in Environmental Sciences (CIRES)
  5. Univ. of Wyoming, Laramie, WY (United States). Dept. of Atmospheric Science
Publication Date:
Report Number(s):
Journal ID: ISSN 2325-1026
Grant/Contract Number:
AC36-08GO28308; AC26-07NT42677
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 5; Journal Issue: 0; Journal ID: ISSN 2325-1026
University of California Press
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); National Oceanic and Atmospheric Administration (NOAA); Colorado Energy Research Collaboratory
Country of Publication:
United States
03 NATURAL GAS; 54 ENVIRONMENTAL SCIENCES; Climate change; Natural gas; Methane; Emissions
OSTI Identifier: