US emissions of methane – a potent greenhouse gas – are 60% higher than EPA thinks

The U.S. oil and gas industry emits 13 million metric tons of methane from its operations each year – nearly 60 percent more than currently estimated by the Environmental Protection Agency, a new study in the journal Science finds.

This means that natural gas, long promoted as a "clean" alternative to other fossil fuels, may not be so clean after all, according to an accompanying article in Science.

Methane is a potent greenhouse gas, with more than 80 times the climate warming impact of carbon dioxide over a 20-year timespan. It is also the main ingredient in natural gas.

The study was led by Environmental Defense Fund researchers, with support from 15 other institutions. "This is by far the most comprehensive body of research of its kind," said the fund's chief scientist and study co-author Steven Hamburg.

The new study estimates the current leak rate from the U.S. oil and gas system is 2.3 percent, versus the current EPA inventory estimate of 1.4 percent. Although the percentages seem small, the volume represents enough natural gas to fuel 10 million homes – lost gas worth an estimated $2 billion.

Researchers measured methane levels in the air around natural gas wells, storage tanks, refineries and underground pipes feeding gas to people’s homes in key gas-producing regions in states including Pennsylvania, Texas, Colorado, Utah, North Dakota and Arkansas.

Methane is emitted during the production and transport of coal, natural gas and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.

However, a gas industry representative questioned the study. "No new measurements were made for this study," said Richard Meyer, the American Gas Association's managing director of energy analysis. "Rather, the authors rely on previous scientific studies and a statistical method that produces higher emissions than previously estimated.

"I have questions about this method and worry that some alternative hypotheses were too readily dismissed," Meyer said.

Seth Whitehead of Energy in Depth, another industry group, called the emissions estimate "exaggerated," but said even if it is accurate, natural gas is still better for the climate than other fuels.

"Leakage rates calculated in the report are well below the threshold for natural gas to maintain its climate benefits over other traditional fuels, and increased use of natural gas is the primary reason U.S. carbon emissions are at a 25-year low," he said.

In an email to USA TODAY, the EPA said that it's looking forward to reviewing the study.

The new findings come as the administration of President Donald Trump works to roll back regulations from former President Barack Obama meant to force the oil and gas industry to cut methane leaks, according to Science.

"Scientists have uncovered a huge problem, but also an enormous opportunity," Hamburg said. "Reducing methane emissions from the oil and gas sector is the fastest, most cost-effective way we have to slow the rate of warming today, even as the larger transition to lower-carbon energy continues."

WPXI