STUDY SUGGESTS EPA METHANE EMISSIONS ESTIMATES TOO LOW

Karen Frantz
GHG Monitor
12/06/13

Emissions of methane, a potent greenhouse gas, may be 1.5 times higher than current Environmental Protection Agency estimates, according to a new study published in the Proceedings of the National Academy of Sciences last week. The study, written by Harvard University’s Scott Miller and 14 other climate scientists, also indicated that methane emissions from agriculture and fossil fuel extraction and processing may be a factor of two or greater than prevailing estimates. “Successful regulation of greenhouse gas emissions requires knowledge of current methane emission sources,” the study says. “Effective national and state greenhouse gas reduction strategies may be difficult to develop without appropriate estimates of methane emissions from [agriculture and fossil fuel] sectors. … These results cast doubt on the U.S. EPA’s recent decision to downscale its estimate of national natural gas emissions by 25–30%.”

The EPA plans to “take a close look” at the study, Administrator Gina McCarthy said on the sidelines of an event the Center for American Progress this week. “The simple fact is that these inventories aren’t precise, they’re opportunities to understand where the opportunities lie and what sectors we need to focus heavily on,” she said. “So as the data gets generated we look at it; we update our inventory all the time. So I’m open to those updates and we’re looking forward to taking a close look at it.” She added that the EPA is looking at opportunities to reduce volatile organic compounds (VOCs), which in turn can reduce methane emissions, but that there are “challenges” associated with regulating methane itself. “But we’re certainly looking at every tool available to EPA, as the president indicated we should,” she said.

The EPA finalized its first air pollution standards for hydraulic fracturing operations in Oil and Gas New Source Performance Standards in April 2012, which will require the capturing of emissions to take effect starting in 2015, and it estimates that the rules will result in the reduction of up to 1.7 million tons of methane annually. Although global emissions of carbon dioxide far outweigh methane emissions, which accounted for just 14 percent of greenhouse gas emissions in 2010, the 100-year warming influence from 1 ton of methane is estimated to be 28 times greater than 1 ton of carbon dioxide.