Natural gas is mostly methane, which is a much more potent greenhouse gas, especially in the short term, with 105 times more warming impact pound for pound than CO2, said Cornell ecologist Robert Howarth. He added that "even small leaks make a big difference" and estimated that as much as 8% of the methane in shale gas leaks into the air during the lifetime of a hydraulically fractured shale gas well, which is up to twice what escapes from conventional gas production.
"The take-home message of our study is that if you do an integration of 20 years following the development of the gas, shale gas is worse than conventional gas and is, in fact, worse than coal and worse than oil," Howarth said. "We are not advocating for more coal or oil, but rather to move to a truly green, renewable future as quickly as possible. We need to look at the true environmental consequences of shale gas."
The American Petroleum Institute (API) blasted the study. "This study lacks credibility and is full of contradictions," said Russell Jones, API senior economic adviser. "The main author is an evolutionary biologist and an anti-natural gas activist who is not credentialed to do this kind of chemical analysis. In supporting documents, the authors admit that the data used was of very low quality. This study is really an exercise in selective data and manipulated methodologies used to reach conclusions that deliberately contradict mainstream science."
On Monday pro-industry blog Energy In Depth (EID) released an "issue alert" seeking to debunk Howarth's research. EID pointed to what it characterized as serious errors in earlier research by Howarth that compared natural gas emissions to those of coal and said his latest research is more of the same, an attempt to "smear shale gas."
EID cited a January memo from former Pennsylvania Department of Environmental Protection (DEP) Secretary John Hanger, who also is a former president of PennFuture, in which Hanger criticizes Howarth's research.
"Natural gas is a cleaner burning fuel and so using more natural gas and renewable energy sources and less coal and oil will save lives and protect the environment," Hanger wrote to DEP staff before leaving the department. "Natural gas emits no soot or mercury, unlike coal. It emits less heat-trapping pollution than coal or oil (a paper that some of you may have seen authored by a professor professing to show carbon emissions are greater from gas is riddled with errors).
"Seventy percent of America's coal-fired power plants have few environmental controls and essentially 100% of them have no controls for heat trapping pollution. Tens of thousands of Americans each year are sickened and killed by soot from diesel trucks and coal plants. Mercury from coal burning contaminates fish, and now one out of six American women has elevated mercury levels because they eat fish."
Howarth, a professor of ecology and environmental biology; Tony Ingraffea, professor of engineering; and Renee Santoro, a research technician in ecology and evolutionary biology, analyzed data from published sources, industry reports and presentations from the Environmental Protection Agency (EPA).
They compared estimated emissions for shale gas, conventional gas, coal (surface-mined and deep-mined) and diesel oil, taking into account direct emissions of CO2 during combustion, indirect emissions of CO2 necessary to develop and use the energy source and methane emissions, which were converted to equivalent value of CO2 for global warming potential.
The study is said to be the first peer-reviewed paper on methane emissions from shale gas, and one of the few exploring the greenhouse gas footprints of conventional gas drilling. Most studies have used EPA emission estimates from 1996, which were updated in November 2010 when it was determined that greenhouse gas emissions of various fuels are higher than previously believed.
"We are highlighting unconventional gas because it is a contemporary problem for us in upstate New York and because there is a big difference between developing gas from an unconventional well and a conventional well, for the mere reason that unconventional wells are bigger," Ingraffea said.
He said hydraulic fracturing lends itself to more leakage because it takes more time to drill and complete the well, requires more venting and produces more flowback waste.
"We do not intend for you to accept what we've reported on today as the definitive scientific study in regards to this question. It's clearly not," Ingraffea said. "What we're hoping to do with this study is to stimulate the science that should have been done before. In my opinion, corporate business plans superseded national energy strategy."
The study is to be published in the May issue of the peer-reviewed journal Climatic Change Letters.