CHARLESTON, W.Va. -- Much more research is needed to determine the extent that greenhouse emissions leak from the processes used to drill for, produce and distribute natural gas, according to a new report that examines the most recent science on the issue.Climate Central, a Princeton, N.J.-based science and journalism organization, said the evidence so far strongly suggests a switch from coal to natural gas is unlikely to provide the 50 percent cut in global warming emissions frequently attributed to such a change in energy supply.Many studies appear to be overly optimistic about the potential benefits of natural gas replacing coal, the group said in a report released last week. Uncertainty about the rate of methane leakage from natural gas processes makes solid projections difficult, the group said."It is impossible to know with confidence what actual leak rates are at a national scale, with the currently available data," said Eric Larson, senior scientist with Climate Central and director of the group's energy program. "But even a relatively low overall methane leak rate of 2 percent may not achieve a 50 percent reduction in greenhouse gas emissions compared to coal in this century because of the greenhouse potency of methane."The Climate Central report comes despite the release in February of the latest U.S. Environmental Protection Agency report on the issue. EPA slashed its estimates of methane emissions from natural gas systems by a third, saying previous government inventories overstated industry leaks.Natural gas industry groups widely praised the new EPA data as proof of the climate change benefits of gas, and that scientists and activists who have expressed concern about the emissions were wrong.But in its report, Climate Central argued that, "this large adjustment from one EPA inventory to the next hints at the uncertainties involved in estimating the national methane leakage rate."In their push for more natural gas, drilling operators are increasingly using a process called hydraulic fracturing, or fracking, which shoots vast amounts of water, sand and chemicals deep underground to break apart rock and release the gas. More frequently, this process also involves drilling down and then turning horizontally to access more gas reserves.
In West Virginia, business and political leaders are eager to expand this practice as companies seek to tap into the vast gas reserves contained in the Marcellus Shale, a formation that stretches across 95,000 square miles from southern New York and into eastern Ohio.Burning coal for electricity produces about twice the carbon dioxide as burning natural gas. But some scientists remain concerned about methane emissions that leak from gas-drilling operations, in part because methane is a more potent greenhouse gas than carbon dioxide.Two years ago, the issue gained much more attention with the publication of a study by Cornell University ecology professor Robert Howarth. That study reported that natural gas could be just as bad -- or worse -- than coal for global warming, especially if the issue is examined based on the short time frame in which scientists believe action is needed to curb global warming.Since then, some other scientists have harshly criticized Howarth's study. But there's also been a lively debate in scientific journals about his results, and about the many variables used to estimate methane emissions from the shale-gas drilling boom across the country.In its new report, Climate Central found that published estimates of methane leak rates range from 1 percent to 8 percent, with peer-reviewed measurements for individual drilling regions as high as 17 percent. EPA's recently revised data cut the agency's national estimate from 2.2 percent to 1.5 percent."Knowing how much methane is leaking from the natural gas system is essential to determining the potential climate benefits of natural gas use," the Climate Central report said.The report found that, "A pervasive lack of measurements makes it nearly impossible to know with confidence what the average methane leak rate is for the U.S. as a whole.
"More measurements, more reliable data, and better understanding of industry practices are needed," the report said.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.