Natural gas leaks from production wells are lower than previous estimates and below the level that would erase the fuel’s climate benefit over coal, according to a University of Texas study backed by both industry and environmentalists.
The study being released today, the first to use actual measurements of emissions, found that 0.42 percent of natural gas produced in the U.S. is released into the atmosphere. A 2010 Cornell University study using data provided by drillers estimated leakage at 0.6 to 3.2 percent.
“The question was, as we bring more natural gas on board, what are the methane emissions, and are they so high that we’re creating a problem for the climate,” Steven Hamburg, chief scientist at the Environmental Defense Fund, said in an interview. “No process is going to be 100 percent tight, and so the question is how low can we get it.”
When it’s burned to produce electricity, natural gas emits about half the carbon dioxide, the main greenhouse gas, as coal. If too much methane escapes, the environmental benefit is lost.
Methane, the main component of natural gas, is 21 times more potent at trapping heat in the atmosphere than carbon dioxide, according to the Environmental Protection Agency. A boom in U.S. natural gas supplies brought on by hydraulic fracturing has opened a debate over whether expanding the use of gas sets back efforts to fight climate change.
The University of Texas worked with the Environmental Defense Fund and nine gas producers including Houston-based Southwestern Energy Co., on the report. Over the course of a year, researchers took direct measurements at 190 well sites in the Gulf Coast, Great Plains, Rocky Mountain and Appalachian regions.
Wenonah Hauter, executive director of Food & Water Watch, a Washington-based environmental group, said too fews wells were part of the study to “draw meaningful conclusions about national emissions.” Companies that allowed methane measurements at their wells were likely to have removed any sources of leaks before researchers arrived.
“This industry-sponsored ‘study’ is more spin than science,” Hauter said in a statement. “The Environmental Defense Fund is running interference for the industry, and the result will be more drilling and fracking around the world.”
Measurements were taken at the well so emissions lost in processing and delivering gas to customers weren’t counted. The University of Texas is conducting studies to measure leakage at other points in the production and delivery process.
Using data from companies, the Environmental Protection Agency in April said that gas leaked from wells in 2011 at a rate of 0.47 percent, compared with 0.42 percent in today’s study.
The University of Texas found leakage at the initial stage of tapping a well when drilling fluids and sand used in hydraulic fracturing, or fracking, returns to the surface was less than found by the EPA. Leakage from equipment at the well pad such a pumps and valves was higher in the University of Texas study.
There are no emissions-control regulations for valves or connectors commonly found at oil or gas wells, according to the Environmental Defense Fund.
“There are emissions that could be reduced from production operations in terms of the equipment and the valves and we need to make sure that happens,” Hamburg said.
The EPA in 2012 issued the first rules to fight air pollution from gas drilling. The regulations require operators to use a technology known as green completions in which escaping gas is captured. The rules, which go into force in 2015, will primarily affect the estimated 13,000 wells a year drilled by fracking to free gas trapped in shale formations.
“It’s very important because it is the one segment of the supply chain that we knew the least about,” Mark Boling, president of Southwestern’s V+ Development Division, said in an interview. “It shows pretty clearly that if you have green completion technology in place, you can reduce potential emissions 99 percent-plus below what they otherwise would be.”
The EPA found that leakage across the entire gas supply chain fell to 1.6 percent in 2011 from 2.4 percent in 2010, Hamburg said. For gas to deliver climate benefits over coal, overall leakage must remain below 3.2 percent.
Lowering that number to 1 percent would have the same climate benefit over the next 20 years as retiring 10 percent of U.S. coal-fired power plants, according to the Environmental Defense Fund.
“The industry has led efforts to reduce emissions of methane by developing new technologies and equipment, and these efforts are paying off,” Howard Feldman, director of regulatory and scientific affairs for the American Petroleum Institute, said in a statement. “Capturing methane is helping operators deliver more natural gas to consumers, creating a built-in incentive to continue reducing these emissions.”
Other companies in the study included Anadarko Petroleum Corporation, BG Group Plc, Chevron Corp., Encana Corp., Pioneer Natural Resources Co., Royal Dutch Shell Plc, Talisman Energy Inc., and Exxon Mobil Corp. The companies were responsible for half of the wells drilled in the U.S. in 2011, and the wells sampled represented 1 percent of gas production.
The companies were not involved in processing data captured at the well sites. The study was peer reviewed and accepted for publication in the Proceedings of National Academy of Sciences, a scientific journal.
Funding for the $2 million study was provided by the Environmental Defense Fund and the 10 companies that participated, Hamburg said.