title: Toward a Functional Definition of Methane Super-Emitters: Application to Natural Gas Production Sites.
abstract: Emissions from natural gas production sites are characterized by skewed distributions, where a small percentage of sites-commonly labeled super-emitters-account for a majority of emissions. A better characterization of super-emitters is needed to operationalize ways to identify them and reduce emissions. We designed a conceptual framework that functionally defines superemitting sites as those with the highest proportional loss rates (methane emitted relative to methane produced). Using this concept, we estimated total methane emissions from natural gas production sites in the Barnett Shale; functionally superemitting sites accounted for roughly three-fourths of total emissions. We discuss the potential to reduce emissions from these sites, under the assumption that sites with high proportional loss rates have excess emissions resulting from abnormal or otherwise avoidable operating conditions, such as malfunctioning equipment. Because the population of functionally superemitting sites is not expected to be static over time, continuous monitoring will likely be necessary to identify them and improve their operation. This work suggests that achieving and maintaining uniformly low emissions across the entire population of production sites will require mitigation steps at a large fraction of sites.
authors.affiliation: †Environmental Defense Fund, 301 Congress Avenue, Suite 1300, Austin, Texas 78701, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Zavala-Araiza
authors.affiliation: †Environmental Defense Fund, 301 Congress Avenue, Suite 1300, Austin, Texas 78701, United States.
authors.forename: David
authors.initials: D
authors.lastname: Lyon
authors.affiliation: †Environmental Defense Fund, 301 Congress Avenue, Suite 1300, Austin, Texas 78701, United States.
authors.forename: Ramón A
authors.initials: RA
authors.lastname: Alvarez
authors.affiliation: †Environmental Defense Fund, 301 Congress Avenue, Suite 1300, Austin, Texas 78701, United States.
authors.forename: Virginia
authors.initials: V
authors.lastname: Palacios
authors.affiliation: †Environmental Defense Fund, 301 Congress Avenue, Suite 1300, Austin, Texas 78701, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Harriss
authors.affiliation: ‡Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas 77004, United States.
authors.forename: Xin
authors.initials: X
authors.lastname: Lan
authors.affiliation: ‡Department of Earth and Atmospheric Sciences, University of Houston, Houston, Texas 77004, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Talbot
authors.affiliation: §Environmental Defense Fund, 18 Tremont Street, Boston, Massachusetts 02108, United States.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Hamburg
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D004777:Environment; D019015:Geologic Sediments / Q000737:chemistry; D008697:Methane / Q000032:analysis*; D059206:Natural Gas / Q000032:analysis*; D013781:Texas
chemical_list: D000393:Air Pollutants; D059206:Natural Gas; D008697:Methane