Animal scientists at UC Davis have been testing different food additives for dairy cows as a way to help reduce belched methane emissions.
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Dairy farms that capture methane from their cows' manure can earn valuable pollution-cutting credits through California's Low Carbon Fuel Standard. Rich Pedroncelli/AP

There are several different greenhouse gases that contribute to raising Earth’s temperature. Carbon dioxide is most often referred to in climate change conversations because of how much we emit and how long it stays in the atmosphere.

Methane comes in as a close second. Its atmospheric lifespan ranges from 10 to 20 years, much shorter than carbon dioxide’s several thousand-year lifespan.

But when it comes to warming, methane gas is 50 to 80 times more powerful than carbon dioxide. Because of that, scientists are looking for ways to limit how much methane we release.

There are many sources of methane, some of which are natural like when biomass decomposes in the world’s wetland regions. Others are manmade in places like oil refineries which often seep methane into the production of fossil fuels.

Some are sort of a mixture of nature and humans. For example, cows.

According to the USDA, there are more than 9 million dairy cows in the United States. Each cow can produce, on average, 220 pounds of methane gas every single year. That accounts for more than 25% of the nation’s methane gas emissions.

But it’s not the cows’ fault. They are known as ‘ruminants’, meaning they have complex, four-chambered stomachs.

“The first stomach chamber they have is called the rumen,” said Dr. Frank Mitloehner, a scientist with UC Davis’ Animal Science department.

That rumen can expand to hold the volume of a standard bathtub. Within the rumen, microbes help to break down what cows are eating.

And their diet is pretty rough. It includes things like almond hulls, straw and residue from cotton plants. The breakdown process releases methane as a byproduct.

The cows then belch that methane and release it into the air.

“Contrary to common belief, it’s not coming out of the back end, it’s coming out of the front end,” Mitloehner said with a smile.

Although, manure is a source of methane as well. One that farmers in California are working to cap, literally, by covering their manure lagoons. That trapped gas can then be turned into transportation fuels.

But back to the belching.

The herd of dairy cows housed at UC Davis is working hard to bring their emissions down. And all they have to do is eat.

Mitloehner and his team have been testing different feeding additives that have been shown to significantly reduce enteric or belched methane. These additives are often natural, being composed of different essential oils or seaweed.

Only a little is needed to be effective. An average adult dairy cow can eat 100 pounds of food per day. But only one gram of additive is used and that little bit goes a very long way.

“On the dairy side, we’ve found approximately 10% reductions of methane,” Mitloehner said.

Other additives can reduce methane emissions by up to 50%. These additives work by either alerting the microbiome in the cows’ guts or by inhibiting methane as a byproduct of digestion.

Those reductions are measured using special feeding stations called head chambers. Cows eat, drink, digest and hang out in these head chambers during testing cycles. As they belch, sensors attached to the head chambers measure methane gas concentrations.

Mitloehner said it takes a bit of training to get the cows used to the head chambers, but ultimately they aren’t stressed by their work environment.

“They can see their peers. They can eat in there, they can drink in there and normally breathe,” Mitloehner said.

The cows don’t know it, but their work is paying off. So far, California has already reduced methane emissions by 25%.

Mitloehner said that the technology exists to eventually help dairy farms become carbon negative, meaning they will actually help to remove carbon from the air rather than create more.

“And that’s what gets me really excited. That a strong reduction of methane can be part of a climate solution and the dairy and the beef sector can be part of that,” Mitloehner said.

Feed additives are already widely used with cattle in Europe. While it’s not forbidden in the United States, it also isn’t approved by the FDA as a method for methane reduction. Mitloehner said that would be the next big step to seeing these additives become more popular.

“I think we should incentivize [dairy farmers] playing that role because these reductions are meaningful, they are immediate and they can really help us getting the job done,” Mitloehner said.

With a third of dairy farms seeking to fill vacancies ahead of calving season, Kiwis are being encouraged to give dairy farming a chance.

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