A recent University study revealed the amount of methane emissions in the United States is higher than previously believed — a lot higher.
The study, which was published Thursday in Science Magazine, reported the actual percentage of methane in the atmosphere is 50 percent greater than current inventories say. In 2011, methane accounted for 9 percent of all human greenhouse emissions, according to the Environmental Protection Agency.
To investigate national methane levels, Eric Kort, assistant professor of atmospheric, oceanic and space sciences, collaborated with co-authors from Stanford University, the Massachusetts Institute of Technology, Harvard University and 11 other institutions across the country.
Kort said the team assessed the last 20 years of methane research to identify how much methane is really being released and how much of this methane comes from the natural gas industry. Methane is the primary component of natural gas, which meets roughly a quarter of the energy demand in the United States.
“Our team reviewed about 200 different papers,” Kort said. “We tried to assess, ‘What do all these studies say, is there a consistent story here?’ What we found is, indeed it looked like official inventories underestimate how much methane is being emitted into the atmosphere.”
Kort attributed the higher amount of released methane, in part, to a very small number of faulty vessels holding natural gas, which can allow significant amounts of methane to leak out into the atmosphere. Kort referred to these leaks as “super-emitters.”
According to one study of natural gas components, “A fraction much smaller than 1 percent is responsible for more than half of the emissions,” Kort said. “You know when you look at these individual studies that a kind of super-emitter problem exists, where a small fraction of sources are responsible for a large amount of the emissions.”
In recent years, natural gas has become a popular, more environmentally friendly replacement for coal as a fuel and heat source. However, natural gas the benefits can be offset by these methane leaks, Kort said. Even so, the study found burning natural gas is still better for the climate than burning coal.
In addition to releases from natural gas, Kort said other sources, such as petroleum systems, livestock and wetlands are also responsible for methane in the atmosphere. As a next step, researchers will attempt to pinpoint the locations of high methane release.
“We’re trying to improve our ability now to use different space and airborne observations to identify regions where emissions are larger than accounted for to identify what source is the cause for that — if it’s coming from cows or oils or gas.”