Three researchers at Cornell University say a controversial study, conducted by their colleagues and stating that shale gas activities posed a more serious threat to global warming than coal, contains serious flaws and should be revisited.
Robert Howarth -- an ecology and biology professor at Cornell -- created a stir in the industry when he and two associates asserted that natural gas drilling and production in shale plays leaked more methane (CH4) than conventional wells and had more of an impact on global warming than carbon dioxide (CO2) released from coal (see Shale Daily, April 13).
"Our review of their own sources finds no evidence that gas is being vented directly into the atmosphere at rates that could justify their conclusions," Cornell researchers Larry Brown, Lawrence Cathles and Andrew Hunter said in a short commentary over the Howarth study. "In contrast, their sources make clear that there are effective technologies to reduce methane emissions to the point they are an insignificant addition to methane's greenhouse combustion footprint, if indeed this is not already the case."
Brown and Cathles are earth science professors at Cornell while Hunter is a lecturer in chemical and biomolecular engineering at the school. Milton Taam, president of Electric Software Inc. of Berkshire, NY, also contributed to the repudiation of the Howarth report.
The four-page short commentary was released on Oct. 4, but a longer version will reportedly be published in a future issue of the peer-reviewed journal Climatic Change Letters, which published the report by Howarth and his associates -- civil and environmental engineering professor Anthony Ingraffea and research aide Renee Santoro -- in its May issue.
"The Howarth study had a big impact on people, and we feel it's a very slanted account of reality," Cathles told Politico, which also reported that he would be in Washington on Tuesday to testify before the Senate Natural Gas Caucus. "It's well done in the sense that it takes quite a lot of effort to dig into it and see why it's slanted and misleading."
Brown, Cathles, Hunter and Taam said the Howarth study erred for three reasons, the first being that the comparison made between coal and natural gas wasn't conducted in terms of how much electricity can be generated by the two fuels individually. Brown and his colleagues reason that CH4 can drive a gas turbine (in a jet engine) and then a steam turbine, so natural gas can generate about twice the amount of electricity as coal.
Secondly, the Howarth study took leaked CH4 figures and converted them to their CO2 equivalents using a 20-year Global Warming Potential (GWP) scale. But GWP doesn't take into account that CH4's lifetime in the atmosphere spans a few decades, while CO2 lasts for centuries. Brown and his colleagues assert that a 100-year GWP scale would be more appropriate for comparison, resulting in a CH4 total that is 3.2 times smaller than the 20-year GWP scale used by Howarth.
Finally, the Howarth study assumed "implausibly high" -- 1.9% of total production -- CH4 leakage rates from natural gas wells during various activities and provided no evidence to back up its claims.
"Not only is this an economic loss no business would contemplate, it represents a risk no company (or their insurer or regulator or rig workers) would accept," Brown and his colleagues said. "The methane release they suggest over a 10 day pre-production period would fill a square mile with an explosive mixture of 5% methane to a height of 176 ft from a single high-volume well."
However, Brown and his colleagues concurred with Howarth that CH4 leakage could affect the impact natural gas has on overall greenhouse gas (GHG) emissions and that better methods for monitoring CH4 leakage needed to be devised.
"From a scientific point of view, if you have this kind of thing out there, it does science a disservice," Cathles told Politico. "It does the university a disservice because people from other points of view can say: 'It's just crazy. We can't believe a word of this.' We felt we needed to make a response from Cornell to this paper that had the Cornell name attached to it."
Blaine Friedlander, spokesman for Cornell University, confirmed for NGI's Shale Daily that Brown and Cathles have written a response to the Horvath study but declined to comment further on the paper because it was embargoed by the Climatic Change Letters. Asked when the paper might be published, Friedlander said late December at the earliest.
"Proofs were submitted to the journal yesterday afternoon and they need to get some more input for the article," Friedlander said Tuesday. "I'm guessing that we're three to four weeks out."
Subsequent studies conducted by the Worldwatch Institute and Deutsche Bank Climate Change Advisors; IHS Cambridge Energy Research Associates; Carnegie Mellon University; Wood Mackenzie; the U.S. Environmental Protection Agency; and the gas-friendly American Clean Skies Foundation criticized the Howarth study for overstating CH4 emissions and said natural gas has fewer GHG emissions than coal (see Shale Daily, Oct. 11; Aug. 25; Aug. 19; May 11; April 21). Clean transportation advocate T. Boone Pickens also took issue with the Howarth report, but comments by Ingraffea have been used by Josh Fox, director of the anti-drilling film Gasland (see Shale Daily, April 20; March 23).
"This latest study from Howarth's Cornell colleagues is an important piece of work in what has been a long line of credible scientists who have debunked his work," Dan Whitten, spokesman for America's Natural Gas Alliance (ANGA), told NGI's Shale Daily on Tuesday. "I think this shows that the scientific community will insist on an adherence to use of credible data when drawing conclusions about such important issues."