The Environmental Protection Agency (EPA) has underestimated methane emissions caused by oil and gas production by as much as 76 percent, according to research published Tuesday in the Journal of Geophysical Research: Atmospheres.
Researchers from Pennsylvania State University collected data in the mid-Atlantic, mid-South and central Midwest of the U.S. from 2017 to 2019, tracking the movement of carbon dioxide, methane and ethane within weather systems. They then studied ethane-to-methane ratios from oil and gas production basins and compared to them an EPA inventory of those emissions.
The assessment found emissions at levels between 48 percent and 76 percent higher than the EPA's estimates.
The researchers said they specifically analyzed ethane because it is only produced alongside certain methane emissions, whereas methane can be produced naturally and by landfills. Ethane also only lingers in the atmosphere for months at a time and offers a clearer picture of how recent the methane emissions occurred.
In a statement to The Hill, the EPA said its greenhouse gas emissions inventory methods are continually updated based on stakeholder feedback.
"Given the variability of practices and technologies across oil and gas systems and the occurrence of episodic events, it is possible that the EPA’s estimates do not include all methane emissions from abnormal events," an agency spokesperson said.
"For many equipment types and activities, the EPA’s emission estimates include the full range of conditions, including 'super-emitters.' For other situations, where data are available, emissions estimates for abnormal events are calculated separately and included in the GHG Inventory," the spokesperson added. "The EPA continues to work through its stakeholder process to review new data from the EPA’s Greenhouse Gas Reporting Program (GHGRP) and research studies to assess how emissions estimates can be improved."
David Lyon, a senior scientist with the Environmental Defense Fund, told The Hill the paper was consistent with other research on underestimations of methane emissions.
"This finding confirms that bottom-up inventory approaches used by EPA greatly underestimate oil and gas methane emissions," Lyon said. "I recommend that EPA and other stakeholders use more measurement data to accurately estimate methane emissions."
The study comes days after the House voted to do away with a Trump administration rule weakening restrictions on methane emissions.
In floor remarks Friday, House Energy and Commerce Committee Chairman Frank Pallone (D-N.J.) called the Trump rule “a thinly veiled attempt to block regulation of the worst oil and gas industry actors at the expense of our health, our safety and our planet.”
—Updated at 4:47 p.m.