WASHINGTON, June 21 (Xinhua) -- The United States oil and gas industry emitted 13 million metric tons of the potent greenhouse gas methane from its operations each year, 60 percent more than estimated by the U.S. Environmental Protection Agency, according to a study published on Thursday in the journal Science.
Researchers found most of the emissions came from leaks, equipment malfunctions and other "abnormal" operating conditions.
The climate impact of those leaks in 2015 was roughly the same as the climate impact of carbon dioxide emissions from all U.S. coal-fired power plants operating in 2015, they found.
"This study provides the best estimate to date on the climate impact of oil and gas activity in the United States," said the paper's co-author Jeff Peischl, a Cooperative Institute for Research In Environmental Sciences (CIRES) scientist working at National Oceanic and Atmospheric Administration (NOAA).
The study assessed measurements made at more than 400 well pads in six oil and gas production basins and scores of midstream facilities.
Methane, the main ingredient of natural gas, is a potent greenhouse gas that has more than 80 times the warming impact of carbon dioxide over the first 20 years after its release.
The new study estimated total U.S. emissions at 2.3 percent of production, enough to erode the potential climate benefit of switching from coal to natural gas over the past 20 years.
The methane lost to leakage is worth an estimated 2 billion U.S. dollars, enough to heat 10 million homes in the United States.
"Natural gas emissions can, in fact, be significantly reduced if properly monitored," said the paper's co-author Colm Sweeney, an atmospheric scientist in NOAA's Global Monitoring Division. "Identifying the biggest leakers could substantially reduce emissions that we have measured."
The research was organized by the Environmental Defense Fund, a non-profit organization, and drew on science experts from 16 research institutions including the University of Colorado Boulder and the University of Texas Austin.
