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Conservation Science for a Healthy Planet

Cows may have contributed to recent uptick in atmospheric methane

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By Chris Mooney September 29  2017 read full Washington Post article here

When it comes to climate change, we know where the most important warming agent — carbon dioxide — is coming from….But the second-most potent greenhouse warming agent — the hard-hitting, if short-lived, gas known as methane — presents more of a mystery. There has clearly been an alarming uptick in atmospheric methane in recent years, following a flattening of concentrations from 2000 to around 2007. But the cause of this particular pattern has been hotly debated, with some blaming the fracked natural gas boom (natural gas is primarily composed of methane) and others pointing to causes such as agriculture.

[Atmospheric levels of methane, a powerful greenhouse gas, are spiking, scientists report]

Now, new research published Thursday in the journal Carbon Balance and Management …. point the finger at agriculture once again. And more specifically, at cattle and other livestock.

“Just from livestock methane emissions, our revisions resulted in 11 percent more methane in a recent year than what we were previously estimating,” said Julie Wolf, lead author of the study who completed the work while a postdoc at the institute and now works at the Department of Agriculture. “It’s not the biggest contributor to the annual methane budget in the atmosphere, but it may be the biggest contributor to increases in the atmospheric budget over recent years…

….Cows and other ruminant animals release methane into the atmosphere as a result of a process called “enteric fermentation” — a technical term that basically refers to the digestive chemistry in the animals’ stomachs. As the Environmental Protection Agency explains, the methane produced in this process “is exhaled or belched by the animal and accounts for the majority of emissions from ruminants.”

Furthermore, the animals’ waste also fills the atmosphere with methane depending on how it is handled, meaning that “manure management” is categorized as a separate source of methane emissions….

Julie Wolf, Ghassem R. Asrar and Tristram O. West. Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock. Carbon Balance and Management. September 201712:16

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