Shale Gas: Cornell's GHG Paper Continues to Attract Criticism

By Steve Everley -- November 2, 2011

For two researchers at Cornell University, it’s turning out to be a very tough year.

Robert Howarth and Anthony Ingraffea released a study this past Spring that found emissions from natural gas produced from shale are worse than coal, based on the global warming potential (GWP) of methane. Since it was released, numerous institutions have weighed in and come to a fairly uniform conclusion: The Howarth/Ingraffea paper simply has too many errors to be credible.

New University of Maryland Study

Nonetheless, ideological opponents of shale gas have continued to wield the Cornell paper as a major weapon against this game changing source of energy. But a new study released by the University of Maryland, The Greenhouse Impact of Unconventional Gas for Electricity Production, suggests that Cornell’s paper has been intellectually superceded.

Among its findings:

“GHG impacts of shale gas are…only 56% that of coal” {p. 1}

“Methane has the ability to trap large amounts of infrared radiation relative to CO₂, but it also has a comparatively shorter lifetime in the atmosphere. As a result, methane’s 100 y GWP is much lower than its 20 y GWP.” {p. 5}

“Two factors lead to an overall carbon intensity advantage for gas during the combustion stage. First, gas releases more energy per unit of carbon emitted. Second, the technology used for combustion of gas is more thermodynamically efficient than that used for coal, enabling a larger amount of chemical potential energy in the fuel to be converted to electricity.” {p. 5}

“[A]rguments that shale gas is more polluting than coal are largely unjustified.” {p. 8}

Other Studies

By reaching the conclusion that the Howarth/Ingraffea study rests on “unjustified” premises, the University of Maryland is joining some pretty elite company, too. For example, here are some conclusions from the August 2011 Carnegie Mellon Report:

“For comparison purposes, Marcellus shale gas adds only 3% more emissions to the average conventional gas, which is likely within the uncertainty bounds of the study. Marcellus shale gas has lower GHG emissions relative to coal when used to generate electricity.”

Lead researcher Paula Jaramillo: “We don’t think they’re using credible data and some of the assumptions they’re making are biased. And the comparison they make at the end, my biggest problem, is wrong.” (as quoted by POLITICO [subs. req’d])

August 2011, Worldwatch Institute study: “[T]he life-cycle GHG footprint of gas is lower than coal under all GWPs tested” (p. 3)

“Despite differences in methodology and coverage, all of the recent studies except Howarth et al. estimate that life-cycle emissions from natural gas-fired generation are significantly less than those from coal-fired generation on a per MMBtu basis.” (p. 9)

August 2011 IHS-CERA Report: “The Howarth estimates assume that daily methane emissions throughout the flowback period actually exceed the wells’ IP at completion. This is a fundamental error, since the gas stream builds up slowly during flowback. Compounding this error is the assumption that all flowback methane is vented… Vented emissions of the magnitudes estimated by Howarth would be extremely dangerous and subject to ignition.”

June 2011, Cornell Professor Lawrence M. Cathles [report submitted for publication]: “[Ingraffea’s and Howarth’s] analysis is seriously flawed in that they significantly overestimate the fugitive emissions associated with unconventional gas extraction…”

“[T]he assumptions used by Howarth et al. are inappropriate and…their data, which the authors themselves characterize as ‘limited’, do not support their conclusions.”

May 2011, U.S. Dept. of Energy Report: “Howarth [and Ingraffea] found a large fraction of produced gas from unconventional wells never made it to end users, assumed that all of that gas was vented as methane, and thus concluded that the global warming impacts were huge. As the [Dept. of Energy] work explains, though, 62% of that gas isn’t lost at all – it’s ‘used to power equipment.’” (Council on Foreign Relations blog, May 20, 2011)

May 2011, Wood Mackenzie Study: “Our analysis indicates that the Cornell study overestimated the average volume of natural gas vented during the completion and flowback stages by 60-65%. We conclude that the Cornell study overestimated the impact of emissionsduring well completions by up to 90%.”

May 2011, Navigant Energy Practice: “[T]he report concludes that the average well [in the Haynesville Shale] spits 250 million cubic feet of methane into the sky. That’s about a million and a half dollars’ worth of gas at today’s prices. … I have to wonder whether the authors have ever seen a working drilling / fracturing operation.” (LINK)

May 2011, Global Warming Policy Foundation, “The Shale Gas Shock” “[Howarth’s conclusion] requires unrealistic assumptions about: the quantity of methane that leaks during fracking, production and transport; the lack of methane leaks from coal mines; the residence time of methane in the atmosphere; and the greenhouse warming potential of methane compared with carbon dioxide. … And Howarth gets his numbers on high gas leakage from shale gas wells from unreliable sources, his numbers on gas leakage from pipelines from long Russian pipelines, and assumes that ‘lost and unaccounted for gas‘ is actual leakage rather than partly an accounting measure. He also fails to take into accountthe greater generating efficiency of gas than coal.” (p. 30)

May 2011, American Gas Association analysis: “Some of the major flaws include … use of data that the authors note is limited and questionable; failure to adequately consider industry control technologies; and misinterpretation of industry terms and datasuch as ‘lost and unaccounted for’ gas.”

April 2011, Clean Air Task Force’s Dave McCabe:“This paper is selective in its use of some very questionable data and too readily ignores or dismisses available data that would change its conclusions.”

April 2011, New York Times reporter Andrew Revkin: “One thing that disturbed me and some of the scientists I consulted was the big gap in the definitiveness of [Cornell’s] abstract summary and the actual paper. … I find that they are more value judgments than scientific judgments.”

John Hanger (former head, Pennsylvania Dept of Environmental Protection: “Professor Horwath’s conclusion that gas emits more heat trapping gas than carbon flies in the face of numerous life cycle studies done around the world.” (April 12, 2011)

“Professor Horwath just adopted an extreme and false assumption of no flaring that conveniently moved the result of his life cycle analysis in the direction that he wanted.” (April 12, 2011)

“Bit by bit the Howarth study is being consigned to the junk heap.” (August 25, 2011)

Natural Resources Defense Council (Dan Lashof): “Moreover, while I can see an argument for using a time horizon shorter than 100 years, I personally believe that the 20-year GWP is too short a period to be appropriate for policy analysisbecause it discounts the future too heavily.  I calculate that over a 50 year period, the GWP of methane would be in the range of 42-56, based on the IPCC and the Shindell et al. analyses.”

Howarth and Ingraffea Self-evaluation

Cornell authors Howarth and Ingraffea have also engaged in some critical self-evaluation:

Howarth: “They are limited data. These are not published data. These are things teased apart out of PowerPoint presentations here and there. So rather than try to extrapolate based on any complicated formula, we’ve ended up simply taking the mean of those values.” (Howarth presentation to colleagues, 22:30, March 15, 2011)

Howarth: “A lot of the data we used are really low quality, but I’m confident that they are the best available data.” (38:50)

Howarth: “Let me just as an aside say that, again, the quality of the data behind that number [methane emissions during well completion] are pretty lousy. You know, they’re these weird PowerPoint sort of things.” (44:15)

Ingraffea: “We are basing this study on in some cases questionable data.”  (38:20)

Ingraffea: “I hope you don’t gather from this presentation that we think we’re right.” (57:15)

Howarth: “We did not look as carefully at coal. … We didn’t put anywhere near the amount of effort into them [coal numbers], but I’m sure they are lower than natural gas.” (39:10 – 40:08)