Natural gas drilling at some sites in southwestern Pennsylvania released 100 to 1,000 times the amount of methane as the Environmental Protection Agency (EPA) has estimated for such operations, according to a new study.
Researchers used a plane that could detect methane emissions and found that a sample of seven gas wells in the Marcellus shale region released an average 34 grams of methane per second. That compares with EPA’s estimates that similar wells should release 0.04 grams to 0.3 grams of methane per second.
The study by researchers at Purdue and Cornell universities was published Monday in the Proceedings of the National Academy of Sciences. It comes as environmentalists are pushing for regulations to curb methane emissions.
Methane is the main ingredient of natural gas and an extremely potent greenhouse gas, far more powerful than carbon dioxide. The Obama administration has signaled an openness to regulating methane emissions, and it released a strategy for reducing emissions last month.
The study points to a weakness in EPA’s method for measuring methane emissions at the ground level, said.
“This indicates that there are processes occurring — e.g. emissions from coal seams during the drilling process — that are not captured in the inventory development process,” Perdue researcher Paul Shepson said in a statement. “This is another example pointing to the idea that a large fraction of the total emissions is coming from a small fraction of shale gas production components that are in an anomalous condition.”
EPA spokeswoman Liz Purchia said the agency is aware that some research comes to different conclusions about methane emissions than EPA’s Greenhouse Gas Inventory.
“Substantial amounts of new information on the oil and gas sector will be made available in the coming years through a number of channels, including EPA’s [Greenhouse Gas Reporting Program], research studies by various organizations, government and academic researchers, and industry,” she said.
New research on the subject is likely to improve EPA’s understanding of it, and the agency will review such research for possible inclusion into its calculations, Purchia said.
The seven high-emitting wells represent 1 percent of wells in southwestern Pennsylvania.