Assessment of methane emissions from the U.S. oil and gas supply chain

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Science  13 Jul 2018:
Vol. 361, Issue 6398, pp. 186-188
DOI: 10.1126/science.aar7204

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  • RE: Natural gas as a bridge fuel to a carbon free future is still a myth
    • Anthony Richard Ingraffea, Professor Emeritus, Cornell University
    • Other Contributors:
      • Renee Santoro, Consultant
      • David Hughes, Scientist, Global Sustainability Research Inc

    Alvarez et al. (1) summarized extensive measurements of methane emissions from oil and gas operations in the U.S. in 2015. They estimated emissions of 13 ± 2 Tg/y, equivalent to a mean of 2.3% of gross U.S. gas production. A national methane emission rate is fundamental to policy decisions concerning switching from other fossil fuels to natural gas. Previous work by Alvarez et al. (2) introduced the concept of technology warming potential (TWP) to relate emission rate to potential climate benefits from fuel switching for auto and truck transportation and for electricity generation.

    Previously published (3) implications of fuel switching on climate benefit were based on estimates of emission rate and other factors needed to use the TWP approach. For example, new, high-efficiency natural gas power plants were shown to produce net climate benefits relative to efficient, new coal plants using low gassy coal on all time frames if leakage in the natural gas system is less than 2.7% from well through delivery at a power plant. Alvarez et al. did not update these implications in (1).

    We have updated the TWP approach based on the new information provided in (1) and (4). Updated methane emission rates are normalized based on natural gas delivered to consumers in 2015, 25 Tcf (5), resulting in rates of 2.9% and 2.4% for well-to-pump and well-to-city gate, respectively.

    Our analysis shows lower rates of emission are now required to show long-term climate benefi...

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    Competing Interests: None declared.