Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 13941-13966, 2017
https://doi.org/10.5194/acp-17-13941-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
23 Nov 2017
Quantifying methane emissions from natural gas production in north-eastern Pennsylvania
Zachary R. Barkley1, Thomas Lauvaux1, Kenneth J. Davis1, Aijun Deng1, Natasha L. Miles1, Scott J. Richardson1, Yanni Cao2, Colm Sweeney3, Anna Karion4, MacKenzie Smith5, Eric A. Kort6, Stefan Schwietzke6, Thomas Murphy7, Guido Cervone8, Douglas Martins9, and Joannes D. Maasakkers10 1Department of Meteorology, The Pennsylvania State University, University Park, PA 16802, USA
2Department of Geography, The Pennsylvania State University, University Park, PA 16802, USA
3NOAA/Earth Systems Research Laboratory, University of Colorado, Boulder, CO, 80305, USA
4National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
5Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
6Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
7Marcellus Center for Outreach and Research, The Pennsylvania State University, University Park, PA 16802, USA
8Department of Geography, The Pennsylvania State University, University Park, PA 16802, USA
9FLIR Systems, West Lafayette, IN 47906, USA
10School of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford Street, Cambridge, Massachusetts 02138, USA
Abstract. Natural gas infrastructure releases methane (CH4), a potent greenhouse gas, into the atmosphere. The estimated emission rate associated with the production and transportation of natural gas is uncertain, hindering our understanding of its greenhouse footprint. This study presents a new application of inverse methodology for estimating regional emission rates from natural gas production and gathering facilities in north-eastern Pennsylvania. An inventory of CH4 emissions was compiled for major sources in Pennsylvania. This inventory served as input emission data for the Weather Research and Forecasting model with chemistry enabled (WRF-Chem), and atmospheric CH4 mole fraction fields were generated at 3 km resolution. Simulated atmospheric CH4 enhancements from WRF-Chem were compared to observations obtained from a 3-week flight campaign in May 2015. Modelled enhancements from sources not associated with upstream natural gas processes were assumed constant and known and therefore removed from the optimization procedure, creating a set of observed enhancements from natural gas only. Simulated emission rates from unconventional production were then adjusted to minimize the mismatch between aircraft observations and model-simulated mole fractions for 10 flights. To evaluate the method, an aircraft mass balance calculation was performed for four flights where conditions permitted its use. Using the model optimization approach, the weighted mean emission rate from unconventional natural gas production and gathering facilities in north-eastern Pennsylvania approach is found to be 0.36 % of total gas production, with a 2σ confidence interval between 0.27 and 0.45 % of production. Similarly, the mean emission estimates using the aircraft mass balance approach are calculated to be 0.40 % of regional natural gas production, with a 2σ confidence interval between 0.08 and 0.72 % of production. These emission rates as a percent of production are lower than rates found in any other basin using a top-down methodology, and may be indicative of some characteristics of the basin that make sources from the north-eastern Marcellus region unique.

Citation: Barkley, Z. R., Lauvaux, T., Davis, K. J., Deng, A., Miles, N. L., Richardson, S. J., Cao, Y., Sweeney, C., Karion, A., Smith, M., Kort, E. A., Schwietzke, S., Murphy, T., Cervone, G., Martins, D., and Maasakkers, J. D.: Quantifying methane emissions from natural gas production in north-eastern Pennsylvania, Atmos. Chem. Phys., 17, 13941-13966, https://doi.org/10.5194/acp-17-13941-2017, 2017.
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Short summary
This study quantifies methane emissions from natural gas production in north-eastern Pennsylvania. Methane observations from 10 flights in spring 2015 are compared to model-projected values, and methane emissions from natural gas are adjusted within the model to create the best match between the two data sets. This study find methane emissions from natural gas production to be low and may be indicative of characteristics of the basin that make sources from north-eastern Pennsylvania unique.
This study quantifies methane emissions from natural gas production in north-eastern...
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