Are gassy cattle a bigger problem than US government thought?
Cattle generate twice as much methane as the EPA supposed, according to a new report. The study's findings may also change assumptions about the safety of extracting natural gas, which consists primarily of methane.
(Page 2 of 2)
The report also called anthropogenic greenhouse gases "the most significant long-term pollution challenge facing America."Skip to next paragraph
Fabien Tepper writes for the Monitor's science desk and weekly magazine. She holds a master's degree in Animals and Public Policy from Tufts University, and a bachelor's degree in art from Swarthmore College.
In Pictures Where to find greenhouse gases
Subscribe Today to the Monitor
After carbon dioxide, methane is the second most prevalent greenhouse gas, and it affects the atmosphere's ability to oxidize other pollutants. According to the report, anthropogenic methane emissions account for 50 to 65 percent of the global methane "budget," the largest portion of which comes from cattle. The natural-gas industry is the next largest source, followed by fermentation in landfills and then coal mining.
So, why are the results of this report so different from government data?
These scientists took a somewhat more on-the-ground (and, it turns out, up-in-the-air) approach. Whereas the EPA bases its estimates on assumed emissions per animal, or per unit of coal or gas sold, these researchers gathered nearly 13,000 measurements of airborne methane from points on the ground, on telecommunications towers, and on airplanes. They also used known information about population density and economic activity to try to determine the relative responsibilities of different methane-generating sectors, in different regions.
But, the MIT Technology Review wrote, the study does not provide "the last word" on methane pollution. "For one thing, it doesn’t directly measure emissions from specific sources, so it doesn’t pinpoint causes of leaks. As more data is gathered, steps can be taken to reduce methane leaks; for example, natural-gas producers and [distributors] could be required to follow best practices."
The EPA said Monday that it is reviewing the Harvard study. "EPA is committed to using the best available data for our inventory and continually seeks opportunities to update and improve our estimates," the agency said in a statement.
Natural-gas industries have been less welcoming of the news.
"Australia's coal seam gas industry has rejected" the study, saying it conflicts with existing information on natural-gas extraction, reports Australia's Sydney Morning Herald.
A source in the US natural gas industry said officials there were not ready to comment on the report.
Just one day before the Harvard report was published, a group of US and Russian scientists published a study in Nature Geoscience, which found that bubbles of ancient methane are surfacing at increasing rates in the Arctic region, as warming oceans thaw underwater permafrost and increasingly fierce storms break up structures that kept them underwater.
"Increasing storminess and rapid sea-ice retreat causing increased CH4 fluxes from the [East Siberian Arctic Shelf] are possible new climate-change-driven processes," the scientists wrote. "Continuing warming of the Arctic Ocean will strengthen these processes."
On Friday, US Defense Secretary Chuck Hagel announced the Pentagon's first-ever Arctic strategy to maintain peace and cleanliness in the rapidly fracturing region, as global warming makes it increasingly vulnerable to drillers and shipping companies.