"Using a plane equipped to measure greenhouse gas emissions in the air, scientists found that drilling activities at seven well pads in the Marcellus shale formation emitted 34 grams of methane per second, on average," significantly higher than EPA estimates of between 0.04 grams and 0.30 grams of methane per second, Banerjee writes.
"Over two days in June 2012, they detected 2 grams to 14 grams of methane per second per square kilometer over the entire area. The EPA's estimate for the area is 2.3 grams to 4.6 grams of methane per second per square kilometer," Banerjee writes. "The researchers determined that the wells leaking the most methane were in the drilling phase, a period that has not been known for high emissions. Experts had thought that methane was more likely to be released during subsequent phases of production, including hydraulic fracturing, well completion or transport through pipelines."
"Last year, researchers from Stanford, Harvard and elsewhere reported in PNAS that methane emissions in the continental U.S. might be 50 percent higher than the EPA's official estimates," Banerjee writes. "Another study by Stanford researchers, published in February in the journal Science, also concluded that the EPA underestimates methane leakage from the natural-gas industry and other sources." (Read more)