New research suggests organizations such as the Environmental Protection Agency (EPA) have underestimated the methane gas emissions in the U.S, especially when it comes to the natural gas industry.
Natural gas consists mainly of methane, a known greenhouse gas, a Penn Energy news release reported.
"People who go out and actually measure methane pretty consistently find more emissions than we expect," lead author of the analysis, Adam Brandt, an assistant professor of energy resources engineering at Stanford University, said in the news release. "Atmospheric tests covering the entire country indicate emissions around 50 percent more than EPA estimates, and that's a moderate estimate."
In order to estimate total methane emission researchers calculate the amount of methane emitted from a particular source, such as a leak in a plant, by the number of sources in the region; the products are then totaled.
The natural gas industry sometimes imposes intentional leaks for safety purposes; but cracks in pipes and other malfunctions can lead to unintentional emissions.
Many studies have looked into emission rates, and found the EPA's estimates were too low. Some used airplanes and towers to measure methane concentrations in the air, and their findings suggest the levels are between 25 and 75 percent higher than the EPA estimate.
These discrepancies may have something to do with the fact that the EPA focused on man-made greenhouse gas emissions as opposed to those that occur naturally.
The recent analysis also suggests studies that looked at high methane emissions in regions with "considerable natural gas infrastructure" do not represent the entire system.
"If these studies were representative of even 25 percent of the natural gas industry, then that would account for almost all the excess methane noted in continental-scale studies," co-author of the study, Eric Kort, an atmospheric science professor at the University of Michigan, said in the news release. "Observations have shown this to be unlikely."
The study found the natural gas industry must clean up its leaks in order to minimize environmental harm. An earlier study found 1,600 leaks, 60 percent of which were linked to only 50 companies.
"Reducing easily avoidable methane leaks from the natural gas system is important for domestic energy security," Robert Harriss, a methane researcher at the Environmental Defense Fund and a co-author of the analysis, said in the news release. "As Americans, none of us should be content to stand idly by and let this important resource be wasted through fugitive emissions and unnecessary venting."
