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Oil, natural gas operations are now top U.S. methane emitters

U.S. greenhouse gas emissions remain flat from 2013 to 2014

by Jeff Johnson, special to C&EN
April 19, 2016

Photo of an oil rig with a sunset behind it.
Credit: Shutterstock
Oil and gas extraction are now the leading source of U.S. methane emissions.

U.S. greenhouse gases emissions held nearly steady from 2013 to 2014, increasingly a mere 1%, according to a newly released annual inventory by the Environmental Protection Agency. But in a key change from previous years, EPA’s report raised methane emissions figures for oil and natural gas drilling and production by 34%. For oil production alone, methane emissions more than doubled.

The agency attributed the increase in methane to new data and more accurate calculations. This sector now accounts for one-third of U.S. methane emission, outpacing landfills and livestock production.

Methane makes up 10.6% by mass of anthropogenic greenhouse gas emissions but is a crucial compound because it has 25 times the global warming potential of carbon dioxide, the greenhouse gas emitted in largest amounts.

The U.S. is experiencing a drilling and production bonanza in oil and natural gas, the latter of which is composed primarily of methane. As a result, natural gas prices have plummeted and supplies have exploded.

Natural gas burns cleaner and produces less carbon dioxide per unit of energy delivered than coal and is displacing coal as the primary fuel for U.S. electricity generation. But high leakage from oil and natural gas wells could change that climate-change advantage.

Consequently, the new methane emission figures for oil and natural gas production are likely to add heat to a long running debate between fossil-fuel advocates and a growing number of atmospheric scientists, who say EPA and industry methane leakage figures have been too low.

“EPA’s methane emissions revisions will nudge natural gas leakage figure upwards,” says Robert Jackson, a Stanford University professor and earth scientist. “Natural gas still looks a little better than coal, particularly when other coal-related air pollution is considered, but the difference is shrinking.”

The oil industry’s American Petroleum Institute disagrees. “EPA has made a significant change in its inventory methodology, and we believe it is seriously flawed,” says vice president Kyle Isakower.

Meanwhile, EPA is considering new regulations for methane emissions, which will focus on oil and gas production facilities.

Overall U.S. emissions in 2014 totaled 6,870 million metric tons of carbon dioxide equivalents, which compares with 7,442 MMT in 2007, the year with nation’s highest recorded releases of greenhouse gases. Electricity generation contributed about 30% of U.S. greenhouse gas emissions, in 2014, followed by transportation at 26% and industrial activities with 21%. The remainder is from agricultural, residential, and commercial sectors.



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