The amount of air pollution associated with hydraulic fractur- ing continues to be a point of contention among environmental- ists, industry leaders and scientists.
Scientists have been divided about the potential air-quality benefits of natural gas compared with coal when fugitive emissions — gas that escapes from drilling operations — are included. Industry officials state that natural gas is the cleanest burning fossil fuel available, while environmentalists have focused on methane being a greenhouse gas that, if unburned, has a greater impact on global warming than carbon dioxide.
A recent study published by professors Francis O’Sullivan and Sergey Paltsev from the Massachusetts Institute of Technology indicated that fugitive emissions of methane from fracking are about 0.5 percent in most shale plays. The highest ratio was 0.8 percent to 1 percent in the Haynesville Shale, because of its “over-pressurized reservoir.”
“Our main estimate of actual fugitive emissions is based on a ‘current field practice’ gas handling scenario, where 70 percent of potential fugitives are captured, 15 percent vented, and 15 percent flared. This we believe is a reasonable representation of current gas- handling practices in the major shale plays,” according to the study.
In addition, the study has found that capturing potential emissions is not without cost, but the costs appear to be relatively modest.
To reduce greenhouse gases “it is clear that increased efforts must be made to reduce fugitive losses,” according to the study.
The study further states that hydraulic-fracturing operations have not altered greatly greenhouse- gas emissions from the natural- gas industry. In addition, the revenues from using green-completion techniques to prevent fugitive emissions cover the cost of using the measures in most cases.
Methane, the main ingredient in natural gas, is a short-lived greenhouse gas many times more potent than carbon dioxide; it’s about 72 times more potent over a 20-year time frame, said Steven Hamburg, chief scientist for the Environmental Defense Fund.
Challenges remain in determining precisely how much methane [natural gas] escapes from wells, said Matt Watson, senior energy policy manager for the EDF.
The defense fund is working to collect data from well sites to determine methane- leakage percentages, he said.
Previous estimates have said that between 1 percent and 7 percent of methane is lost to leaks, Watson said.
“The truth is we really don’t know,” he said. “We are trying to come up with empirical data, not estimates based on manufacturer specifications.”
The study will examine methane leakage during production, from processing and gathering lines, transmission and storage, local distribution and natural- gas vehicles and fueling stations.
“EDF is actively campaigning to ensure that fugitive methane emissions from the natural gas industry are less than 1 percent of production in order to ensure that the climate benefits of natural gas are maximized,” he said.
The MIT study, as opposed to those done previously, researches industry practices — not theoretical ideas, said Dan Alfaro, spokesman for Energy-In-Depth, an oil -and-gas industry outreach group.
“Advanced technologies and green-completion practices have produced greenhouse gas emissions far lower than what we have seen presumed in some of these prior studies .. ,” he said.
Companies across the country are using green- completion methods, which involve no fugitive emissions, in areas with a developed infrastructure, which is one reason why greenhouse gas emissions are lower than previous estimates, Alfaro said. Green completion is not possible without pipeline infrastructure.
“Some of the previous studies we’ve seen have erred in assumptions made regarding the actual practices used by the industry in handling emissions, which is why we have seen these studies rebuked and debunked so often,” he said.