North America Methane Leaks Higher Than Previous Estimates

U.S. Environmental Protection Agency (EPA) estimates of methane emissions have been underestimated over the past two decades, according to a study published Friday in the journal Science.

In the new analysis, “Methane Leakage from North American Natural Gas Systems”, researchers compared findings from over 200 studies ranging in scope from local gas processing plants to total emissions from the United States and Canada.

“Actual measurements consistently indicate that methane emission levels are about 50 percent higher than what our national accounts suggest,” said MIT Energy Initiative Director of Research Francis O’Sullivan in a Feb. 13 press release.

O’Sullivan was part of the team of authors who worked on the study, which included representatives from seven universities, national laboratories, federal government bodies and other groups.

“It appears certain that some of this additional methane is from the natural gas system, though likely not all due to the poor state of science surrounding other significant sources,” O’Sullivan commented.

Total methane emissions are typically estimated by multiplying the amount of methane thought to be emitted by a particular type of source, such as natural gas processing plants or belching cattle, by the number of that source type in a region or country. The products are then totaled to estimate all emissions.

Natural gas consists primarily of methane. Methane is emitted intentionally and unintentionally from natural gas infrastructure for safety purposes and through faulty valves and pipeline cracks. In the 1990s, the EPA established emission rates of particular U.S. gas industry components, from wells to burner tips. Since then, many studies have tested gas industry components to determine if the EPA emission rates are accurate; a majority of these studies have found the EPA rates to be too low.


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