Anyone who has spent time at a dairy or stockyard knows that cows are gassy creatures. And all that gas takes a toll on the environment: Cows emit enormous amounts of methane, a powerful greenhouse gas that contributes significantly to climate change. But you might be surprised to learn that the majority of methane emitted by cows comes from their mouths, not their rears.

Cattle are responsible for about two-thirds of anthropogenic greenhouse gas emissions from livestock, according to a report by the United Nations Food and Agriculture Organization. That works out to nearly 10 percent of global emissions overall. As a greenhouse gas, methane is 25 times more powerful than carbon dioxide, because it's much better at trapping radiation. The problem is so serious that governments around the world are looking for new ways to cut cattle methane production. Now a team of researchers in Denmark is testing the potential of oregano—that’s right, the herb you shake on your pizza—to do the job.

Scientists from Aarhus University have just launched a four-year study to gauge the effectiveness of a particularly potent type of Greek oregano in reducing methane emissions from dairy cow belches by adding it to the cows’ feed.

Cows, like sheep, goats, buffalo, and camels, are ruminants, a type of animal with a unique digestive system that includes a large stomach chamber called the rumen. There, microbes break down food through fermentation, helping cows to survive on tough plant material that other animals cannot eat. But some of those microbes produce methane—a lot of it—that the cows belch out before it can work its way through the rest of their digestive systems.

“The contribution of methane gases from ruminants to global warming is considerable, and a reduction in methane emission from ruminants would be of great importance—not only for organic agriculture but worldwide,” project manager Kai Grevsen said in an email to mental_floss. Grevsen is a senior researcher in the Aarhus University Department of Food Science.

Conventional farmers already use nitrates, antibiotics, fats, and starches to reduce the methane released when cows pass gas. But nitrates and certain fats aren’t permitted under European Union and Danish organic rules.

In recent years, scientists have also experimented with a number of other chemical methane inhibitors, but concerns about animal health, food safety, and the environmental impact have stymied commercial use.

Earlier research led by Penn State scientists suggested that oregano could cut cows’ methane emissions up to 40 percent. But the type of oregano used in those experiments wasn’t as strong as the current project’s organic Greek oregano, which has higher concentrations of essential oils and antimicrobial properties.

“The theory is that the essential oil in oregano … is killing or, at least, weakening the population of the methane-producing microbes more than all the other ‘good’ microbes, and therefore less methane is produced,” Grevsen says.

Most of the earlier experiments were also performed in vitro, in a lab. The Danish experiment will place cows from three organic dairy farms in specially designed, airtight chambers where researchers can monitor the cows’ digestion, take samples of the microbes, and measure all the gases they emit. The cows’ milk will also be tested for quality and taste.

Part of the challenge will be to determine the right amount of oregano to control the methane-producing microbes without causing adverse effects to the cows’ normal digestion, Grevsen says. 

Oregano isn’t the only promising effort to control cows’ methane production. There’s a growing body of research looking into solutions that range from new types of feed to experimental vaccines to genetic modification that would breed less gassy cows. But the oregano supplement, if successful, might be one of the most straightforward, environmentally friendly solutions yet.

“The Greek oregano is relatively simple to grow,” Grevsen says. “It’s a perennial 4–5 year crop that has high biomass yield and can be harvested like hay.”

If the Danish research shows positive results, it could be good news for the United States, which has set a goal of cutting methane emissions from dairy cows 25 percent by 2020.

There’s also evidence that oregano may be associated with increased milk production and quality. Stay tuned to find out whether “oregano-fed cows” becomes the next big food trend.