A dash of oregano does more than make pizza taste delicious: it also can reduce the amount of methane in cow burps, new research shows.

Scientists have been trying to decrease methane from livestock for years; methane is over 20 times more potent than carbon dioxide (CO2) as a greenhouse gas, and cows in the U.S. emit about 5.5 million metric tons of methane per year. Scientists have tried vaccines, breeding, antibiotics, and other dietary supplements like garlic or fumaric acid (found in lichens and moss).

A new possibility: common oregano.

Alexander Hristov, assistant professor of dairy nutrition at Penn State, spent six years in his lab trying various natural methods to cut cows' methane belches. Eventually, oregano surfaced as the most effective methane suppressant.

Hristov then took oregano into the field, "and we saw the same effect there," he says, cutting the cows' emissions by 40 percent.

Decreasing methane production in dairy cows, the type Hristov worked with, also increases their milk production. "Methane is an energy loss to the animal, and if you reduce methane production, there is energy available for the animal" to make milk, he explains.

The advantage of oregano: If Hristov's team can isolate the compound inside the oregano and synthesize it in the lab, it'll be very cheap. "I don't think just feeding oregano to nine million cows in the U.S. is going to be very cost-effective," he says.

But if we could--or if Hristov gets an oregano supplement to market--the U.S. would cut its cattle methane emissions by 2.2 million tons.

Of course, the greenest way to cut methane emissions from cows is to have fewer of them: meat-eaters are responsible for the equivalent of 1485 kilograms of CO2 per year more than a vegan eating the same number of calories. (But carnivores, take note: just cutting out red meat in favor of fish, poultry, and eggs is a great way to cut emissions--beef, pork and lamb are the big culprits. Or switch to grass-fed and free-range, which often takes less energy to raise.)

Until that happens, Hristov and other researchers all over the world will carry on, always trying to make their cows less gassy.

Hristov and colleagues are presenting their work at the Greenhouse Gases and Animal Agriculture Conference in early October.

Rachel Kaufman is a writer and editor covering science and the environment, emerging technology, and a potpourri of other topics. Her freelance writing career has taken her inside Victorian-era "castles," French patisseries, and a haunted train tunnel, and in addition to her work for National Geographic News, her byline has appeared in the Washington Post,  ScientificAmerican.com, and CNN/Money. Rachel grew up outside Minneapolis and received her B.A. in English and journalism from Adelphi University on Long Island, but finds her constitution (and temperament) far better agrees with the swampy air of her adopted hometown, Washington D.C. Her blog and portfolio can be found at http://readwriterachel.com and she tweets about science, journalism, and video games at @rkaufman.