The Barnett Shale is more than 7,000 feet below the surface and is comprised of dense non-permeable rock. According to Dr. Ken Morgan, a geologist at Texas Christian University, “Solid hard rocks that are 7000 feet down don’t subside. You have more than a mile of solid rock that holds it all up. Subsidence occurs when you have loose, soft materials like in Houston (sands, clays, etc.) but not in cemented hard rocks like the Barnett Shale.”
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Critique of the Environmental Defense Fund’s paper on methane leakage
Critique of the Environmental Defense Fund’s paper on methane leakage
The fact that natural gas is the cleanest-burning fuel, emitting half of the carbon of coal, is undisputed. After all, the chemical structure of methane, the primary component of natural gas, is CH4: one carbon molecule combined with 4 hydrogen molecules. By contrast, coal is 50-100% carbon by mass, with the rest being hydrogen, nitrogen and oxygen and sulfur. So, the environmental benefits of natural gas vehicles are obvious. This is why the Honda Civic GX, which runs on compressed natural gas or CNG has been deemed the “greenest car in America” for the last 8 years, beating out all hybrids and plug-in electric cars.
However, a recent study by the Environmental Defense Fund (EDF), entitled “Greater focus needed on methane leakage from natural gas infrastructure,” called into question the climate impacts of natural gas vehicles. The paper draws this conclusion: “Given EPA’s current estimates of [methane] leakage from natural gas production and delivery infrastructure, in addition to a modest [methane] contribution from the vehicle itself (for which few empirical data are available), CNG-fueled vehicles are not a viable mitigation strategy for climate change (EDF paper, page 2).
But in the EDF press release the conclusions are less clear: “the paper does not draw hard and fast conclusions about the future implications of any kind of fuel shifting, nor does it answer the question of whether natural gas generation or natural gas-powered vehicles will be better or worse for the climate.” The reason for this walk-back is that the authors recognized that their paper is based on poor data from the EPA. In their white paper entitled “Greenhouse Gas Emissions Reporting from the Petroleum and Natural Gas Industry”, 2010”) the EPA noted that their own analysis is “weakened by the paucity of empirical data addressing CH4 emissions through the natural gas supply network.” The EPA goes on to note “these estimates are based mostly on emissions factors available from two major studies … conducted in the early and late 1990s respectively.” (EPA, p. 7-8).)
It is unfortunate that EDF did not have a copy of the publically available 2011 report by URS for if they did they would have realized just how unreliable EPA’s methane emission estimates are for shale gas wells. If EDF had monitored the public comment docket for the EPA’s oil and gas air rule, where these very emissions estimates were challenged, they would have found real data for over 1,500 wells, from 8 companies, across 10 production basins, that demonstrate that EPA’s well completion emissions estimate is 1,200% too high.
EDF recognizes the need for better emissions data than the EPA estimates. It was available from the natural gas industry all along and EDF should have used it before making faulty conclusions about the viability of NGVs. If they had, the outcome of the study would be vastly different. NGVs would have been shown to make the positive contribution to the environment that they in fact do.




