Study citing shale gas 'footprint' disputed
The Cornell findings said the environmental effects could be as bad as coal's. Producers question the data.
PITTSBURGH POST-GAZETTE
A Cornell University study is drawing criticism from the Marcellus Shale industry by concluding that methane produced from shale gas has as large a "greenhouse gas footprint" as coal, or larger.
The study, led by Robert W. Howarth, a professor of ecology and environmental biology, says methane leaking or venting from Marcellus Shale wells - and during the processing and transportation of natural gas - will contribute "substantially to the greenhouse gas footprint of shale gas" in the next 20 years.
Published this week in the journal Climactic Change Letters, the study focuses on a 20-year period for methane's greenhouse-gas effect because the gas doesn't last in the atmosphere as long as carbon dioxide produced by coal-burning. Carbon dioxide can remain 10 times longer in the atmosphere, but the study says methane can be more damaging to the climate in the short run.
According to the study, 3.6 to 7.9 percent of shale gas is lost to the atmosphere by venting from backflow water released from wells and pressure valves, along with leaks that can occur in as many as 150 pieces of equipment used to produce, process, and ship gas and losses along the gas pipelines to market.
The study said the totals were calculated from various sources but reflected how much methane escapes into the atmosphere from venting or leaking over the lifetime of a well.
"The higher emissions from shale gas occur at the time wells are hydraulically fractured" - the injection of liquids and sand under high pressure to break up rock formations deep underground to release natural gas. Methane mixed with fluids flowing back from the well can escape into the atmosphere.
It also can escape during other follow-up procedures after fracturing occurs, the study says.
The greenhouse effect of methane from shale gas, the study says, is at least 20 percent greater than the effect from coal, and could be twice as much.
As a result, Howarth said in an interview, natural gas "is not as clean as advertised," and using it as a transitional energy source to break our dependence on coal might not be a wise energy policy.
The natural gas industry questioned the accuracy of the study's conclusions.
Energy in Depth, representing the nation's independent natural gas and oil producers, issued five major criticisms of the study, ranging from what it describes as the authors' previous wavering about data used in the study, acknowledgement of errors, and restatements of findings.
The producers also criticize the study's use of the 20-year period to analyze greenhouse gases rather than 100 years. They also said the study used questionable data along with assumptions that do not stand up to scrutiny, while contending Howarth has long-held biases against the industry.
Matt Pitzarella, spokesman for Range Resources, a major Marcellus Shale drilling company based in Cecil, Washington County, said the industry would lose $6 billion a year if up to 7.9 percent of shale gas were being lost to the atmosphere. Such releases would not only pose safety risks, but mean a great loss in revenues for drilling companies.
Jan Jarrett, president and chief executive officer of Citizens for Pennsylvania's Future, a statewide environmental advocacy organization, said she respected the research of Howarth and his Cornell team.
But she also noted that the authors readily admit that some information used is questionable even if it is the best available data, making further studies necessary.