By Daniel Trotta
NEW YORK (Reuters) - An abundant source of U.S. natural gas widely seen as a cleaner alternative to oil and coal is in reality the fossil fuel that creates the most greenhouse gas emissions, a study concludes.
The paper led by Cornell University ecology professor Robert Howarth raised howls of protest from the gas industry, which said the document was political.
The study contends that so much methane escapes from the extraction of shale gas over the life of a well that it allows more heat-trapping greenhouse gas into the atmosphere than coal.
The report acknowledged that natural gas is cleaner to burn than other fuels but that greater pollution derives from leakage, whether accidental or purposely designed to relieve well pressure.
Improved technology could solve the problem but Howarth in an interview doubted whether that was economical considering stubbornly low natural gas prices. A North American boom in the production of shale gas, billed as an alternative to foreign oil, has depressed gas prices even while oil has soared.
Industry representatives criticized the work as sloppy and incomplete advocacy against shale gas. The shale boom previously had raised more alarm from environmentalists because of the threat of chemicals seeping into ground water through the drilling process known as hydraulic fracturing, or "fracking."
For an index of shale gas companies, double-click on.
Some 3.6 percent to 7.9 percent of the methane from shale gas production leaks into the atmosphere, releasing a greenhouse gas that is especially potent over the first 20 years, the study said.
"The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years," said the study, which can be seen on http://www.eeb.cornell.edu/howarth/Howarth%20et%20al%20%202011.pdf.
"Compared to coal, the footprint of shale gas is at least 20 percent greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years."
Such conclusions break conventional thinking and sound outrageous to industry representatives, who said Howarth exaggerated the amount of highly valuable gas purportedly allowed to escape.
"The problems with the study boil down to two basic areas: the data and the assumptions. Apart from that, Mrs. Lincoln, it's a terrific study," Chris Tucker, spokesman for the industry group Energy In Depth, said in a statement.
"This isn't a serious academic pursuit, but rather a serious political one," Tucker said.
A more detailed response can be seen at http://www.energyindepth.org/2011/04/five-things-to-know-about-the-cornell-shale-study/.
Howarth defended his work as meeting strict academic and scientific standards.
"It's being published in a highly respected journal and has been rigorously peer-reviewed," Howarth said. "This is not advocacy. This is science."
The criticism of Howarth work began more than a year ago when he reported preliminary findings in a two-page summary. Since then Howarth has issued periodic updates.
The final paper, co-written with Renee Santoro and Anthony Ingraffea, had been due to be published in the journal Climatic Change Letters on Thursday but was made available on Tuesday after it was released by The Hill newspaper.
(Reporting by Daniel Trotta; editing by Alden Bentley)