Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Jan 16:8:14012.
doi: 10.1038/ncomms14012.

Super-emitters in natural gas infrastructure are caused by abnormal process conditions

Daniel Zavala-Araiza  1 , Ramón A Alvarez  1 , David R Lyon  1 , David T Allen  2 , Anthony J Marchese  3 , Daniel J Zimmerle  4 , Steven P Hamburg  1
Affiliations

Super-emitters in natural gas infrastructure are caused by abnormal process conditions

Daniel Zavala-Araiza et al. Nat Commun. .

Abstract

Effectively mitigating methane emissions from the natural gas supply chain requires addressing the disproportionate influence of high-emitting sources. Here we use a Monte Carlo simulation to aggregate methane emissions from all components on natural gas production sites in the Barnett Shale production region (Texas). Our total emission estimates are two-thirds of those derived from independent site-based measurements. Although some high-emitting operations occur by design (condensate flashing and liquid unloadings), they occur more than an order of magnitude less frequently than required to explain the reported frequency at which high site-based emissions are observed. We conclude that the occurrence of abnormal process conditions (for example, malfunctions upstream of the point of emissions; equipment issues) cause additional emissions that explain the gap between component-based and site-based emissions. Such abnormal conditions can cause a substantial proportion of a site's gas production to be emitted to the atmosphere and are the defining attribute of super-emitting sites.

PubMed Disclaimer

Conflict of interest statement

Four co-authors (D.Z.-A., R.A.A., D.R.L. and S.P.H.) work for Environmental Defense Fund (EDF), a non-profit organization funded by philanthropic contributions, which does not accept donations from the oil/gas industry in accordance with its corporate donations policy (). The other co-authors were lead investigators in separate projects focused on quantifying methane emissions from the U.S. natural gas supply chain, sponsored in part by EDF (D.T.A., A.J.M. and D.J.Z.), companies in the oil and gas industry (D.T.A., A.J.M. and D.J.Z.) and the US Department of Energy (A.J.M. and D.J.Z.). One author (D.T.A.) has served as a paid Special Governmental Employee, while chair of the EPA's Science Advisory Board, and has consulted for multiple companies, including Eastern Research Group, ExxonMobil and Research Triangle Institute. Another author (S.P.H.) serves as a paid Special Governmental Employee, while serving on the EPA's Science Advisory Board.

Figures

Figure 1
Figure 1. Classification of sites in terms of magnitude of emissions and component behaviour.
The vertical axis classifies sites in terms of magnitude of total site-level emissions (where 26 kg CH4 per hour is the threshold for higher emitters). The horizontal axis classifies sites in terms of component behaviour that results in emissions (emissions by design versus unintended). The bullets in each quadrant indicate the components that were included in our component-based aggregation model; these represent all known sources of emissions on natural gas production sites in the Barnett Shale. The shaded quadrant accounts for the existence of abnormal process conditions that result in high, unintended emissions, the defining characteristic of super-emitting sites.
Figure 2
Figure 2. Distribution of methane emissions from production sites in the Barnett Shale.
(a) Cumulative percentage of sites as a function of the emission rate per site. In (b) we show the 5% of sites with highest emissions; (c) cumulative emissions as a function of emission rate per site. Blue lines represent each of 104 Monte Carlo iterations from the component-based aggregation reported in this work; orange lines represent the site-based results derived from Zavala-Araiza et al.; vertical lines represent the 99th percentile of site emissions in Zavala-Araiza et al. (26 kg CH4 per hour). Inset text show ratios between site-based and component-based estimates for given metrics.
See this image and copyright information in PMC

References

    1. Allen D. T. et al.. Measurements of methane emissions at natural gas production sites in the United States. Proc. Natl Acad. Sci. USA 110, 17768–17773 (2013). - PMC - PubMed
    1. Allen D. T. et al.. Methane emissions from process equipment at natural gas production sites in the United States: pneumatic controllers. Environ. Sci. Technol. 49, 633–640 (2015). - PubMed
    1. Allen D. T. et al.. Methane emissions from process equipment at natural gas production sites in the United States: liquid unloadings. Environ. Sci. Technol. 49, 641–648 (2015). - PubMed
    1. Lamb B. K. et al.. Direct measurements show decreasing methane emissions from natural gas local distribution systems in the United States. Environ. Sci. Technol. 49, 5161–5169 (2015). - PubMed
    1. Mitchell A. L. et al.. Measurements of methane emissions from natural gas gathering facilities and processing plants: measurement results. Environ. Sci. Technol. 49, 3219–3227 (2015). - PubMed

LinkOut - more resources