Title: Exploratory study of atmospheric methane enhancements derived from natural gas use in the Houston urban area

Abstract

Here, the extensive use of natural gas (NG) in urban areas for heating, cooking and as a vehicular fuel is associated with potentially significant emissions of methane (CH₄) to the atmosphere. Methane, a potent greenhouse gas that influences the chemistry of the atmosphere, can be emitted from different sources including leakage from NG infrastructure, transportation activities, end-use uncombusted NG, landfills and livestock. Although significant CH₄ leakage associated with aging local NG distribution systems in the U.S. has been reported, further investigation is required to study the role of this infrastructure component and other NG-related sources in atmospheric CH₄ enhancements in urban centers. In this study, neighborhood-scale mobile-based monitoring of potential CH₄ emissions associated with NG in the Greater Houston area (GHA) is reported. A novel dual-gas 3.337 μm interband cascade laser-based sensor system was developed and mobile-mode deployed for simultaneous CH₄ and ethane (C₂H₆) monitoring during a period of over 14 days, corresponding to ~ 90 hours of effective data collection during summer 2016. The sampling campaign covered ~ 250 road miles and was primarily concentrated on eight residential zones with distinct infrastructure age and NG usage levels. A moderate number of elevated CH₄ concentration events (37 episodes) with mixingmore » ratios not exceeding 3.60 ppmv and associated with atmospheric background enhancements below 1.21 ppmv were observed during the field campaign. Source discrimination analyses based on the covariance between CH₄ and C₂H₆ levels indicated the predominance of thermogenic sources (e.g., NG) in the elevated CH₄ concentration episodes. The volumetric fraction of C₂H₆ in the sources associated with the thermogenic CH₄ spikes varied between 2.7 and 5.9%, concurring with the C₂H₆ content in NG distributed in the GHA. Isolated CH₄ peak events with significantly higher C₂H₆ enhancements (~11 %) were observed at industrial areas and locations with high density of petroleum and gas pipelines in the GHA, indicating potential variability in Houston’s thermogenic CH₄ sources.« less

Authors:

Sanchez, Nancy P. ^[1]; Zheng, Chuantao ^[2]; Ye, Weilin ^[3]; Czader, Beata ^[1]; Cohan, Daniel S.  ^[1];

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Tittel, Frank K. ^[1]; Griffin, Robert J. ^[1]

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+ Show Author Affiliations

1. Rice Univ., Houston, TX (United States)
2. Rice Univ., Houston, TX (United States); Jilin Univ., Changchun (China)
3. Rice Univ., Houston, TX (United States); Shantou Univ., Shantou (China)

Publication Date:

Thu Jan 04 00:00:00 EST 2018

Research Org.:

Rice Univ., Houston, TX (United States)

Sponsoring Org.:

USDOE Advanced Research Projects Agency - Energy (ARPA-E)

OSTI Identifier:

1435611

Report Number(s):

DOE-MAXION-00538-13
Journal ID: ISSN 1352-2310; PII: S1352231018300013

Grant/Contract Number:  

AR0000538

Resource Type:

Accepted Manuscript

Journal Name:

Atmospheric Environment (1994)

Additional Journal Information:

Journal Name: Atmospheric Environment (1994); Journal Volume: 176; Journal Issue: C; Journal ID: ISSN 1352-2310

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 03 NATURAL GAS; Natural gas; Methane emissions; Natural gas distribution systems; Mobile-mode field monitoring; Thermogenic methane emission sources