The Environmental Protection Agency may have overlooked the real culprits in its recent crackdown on methane emissions from fossil fuels: rice farmers and cows.
A newly released study led by the National Oceanic and Atmospheric Administration attributed the increase in global atmospheric methane since 2007 to microbial sources, including rice paddies, livestock, decaying vegetation in wetlands, even termites, not fossil fuels.
That finding comes even though scientists also concluded that methane emissions from oil, coal and natural gas are 20 to 60 percent higher than previously estimated.
“We recognize the findings might seem counterintuitive — methane emissions from fossil fuel development have been dramatically underestimated — but they’re not directly responsible for the increase in total methane emissions observed since 2007,” said lead author Stefan Schwietzke of the Cooperative Institute for Research in Environmental Sciences [CIRES] at the University of Colorado Boulder, working in NOAA’s Earth System Research Laboratory.
The report, published Thursday in the journal Nature, provided fodder to those challenging the EPA’s methane rule, released in May, which seeks to cut methane emissions from fossil-fuel sources by 40 to 45 percent by 2025 from 2012 levels in order to combat climate change.
At least 15 states have filed a lawsuit seeking to block the methane rule, led by top oil-and-gas producers North Dakota and Texas.
Kathleen Sgamma, Western Energy Alliance vice president for government and public affairs, called on the Obama administration to “recognize good science, and stop the climate change orthodoxy that actually punishes a real solution for climate change.”
The report found that the industry had reduced methane leaks from oil and gas facilities from 8 percent of production to about 2 percent.
Meanwhile, natural-gas development has skyrocketed by 47 percent while methane emissions have fallen by 21 percent since 1990, she said.
“The recent NOAA study and several others show that increased global methane emissions are not from oil and natural gas production, but from natural sources like wetlands and natural seeps,” Ms. Sgamma said in a statement. “It’s time for the administration to stop punitive regulation on the only industry that captures methane in substantial quantities and puts it to beneficial use.”
Methane is the second-leading contributor to greenhouses gases, behind carbon dioxide, and while not as long-lived, “methane is 28 times more effective in trapping heat in the Earth’s atmosphere over a 100-year time span,” according to NOAA.
The NOAA/CIRES study, which supports the conclusions of previous research by scientists in London and New Zealand, found microbial sources are responsible for 58 to 67 percent of the 623 million metric tons of methane emitted by all sources each year.
The second-largest source was fossil-fuel development, which is responsible for about 20 to 25 percent. That figure rises to 26 to 35 percent when including “natural geological seepage.”
“We find that total fossil fuel methane emissions (fossil fuel industry plus natural geological seepage) are not increasing over time, but are 60 to 110 per cent greater than current estimates owing to large revisions in isotope source signatures,” said the study.
From 2007 to 2013, total emissions from all sources increased by about 28 million tons, which the scientists attributed to microbial sources.
“We believe methane produced by microbial sources — cows, agriculture, landfills, wetlands and fresh waters — are responsible for the increase, but we cannot yet pinpoint which are the primary drivers,” Mr. Schwietzke said.
“If the methane is mainly coming from cows or agriculture, then we could potentially do something about it,” he said. “If it’s coming from decaying vegetation in wetlands or fresh waters, then a warming climate could be the culprit, which means that it could be part of a self-reinforcing feedback loop leading to more climate change. Those are big ifs, and we need to figure them out.”
Rep. Lamar Smith, chairman of the House Science, Space and Technology Committee, blasted the EPA’s methane rule in a Sept. 15 hearing, calling the regulation an example of how the EPA “cherry-picks the science that fits its agenda and ignores the science that does not support its position.”