One Scientist’s Ambitious Plan to Achieve Global Cooling With Cattle

Cows could be a climate change solution — if we take the science seriously

Photo: Peter Cade/Getty Images



“Because it really is a major deal that agriculture can contribute here.”

Adding insult to injury, Burger King doesn’t know which end of the cow to focus on.

It’s the burps, BK, not the farts. The burps.

Frank Mitloehner, PhD, a University of California, Davis animal science professor and air quality expert, shared strong words about the campaign. “Nearly all enteric methane from cattle is from belching,” he tweeted in response. “Suggesting otherwise turns this serious climate topic into a joke.” Cattle, he argues, can cool the planet — herd sizes, efficient production methods, and burp management are key — and it’s past time for the conversation to shift toward exploring how their emissions could be manipulated in favor of global cooling.

“This is why I have a beef [with] making a silly story out of this,” Mitloeher tells OneZero. “Because it really is a major deal that agriculture can contribute here.”

One of the best parts of growing up a farm kid is experiencing science firsthand — for instance, by having a cow belch in your face. My first job was feeding calves, and I raised heifers for the neighboring dairy starting at age 12 to put myself through college before starting my own farm, so it’s safe to say I’ve had more than my fair share of experience with cow “eructation” (the fancy-pants name for cow belching).

Cows burp dozens of times a day as part of the natural cycle of the ruminant digestive system. When a cow gulps down a mouthful of grass, its digestive process starts in the first of four stomachs, the rumen. Capable of holding up to 25 gallons, about the size of your bathtub, the rumen is chock full of microbes. The whole thing acts like a giant fermentation vat for cellulose-based materials, like grass and hay, the stuff humans can’t digest. Fermentation creates gas — in the case of cows, about 30 to 50 quarts of gas per hour. Ouch.

That’s where the burps come in. A cow burp itself is not unpleasant; it’s sort of sweet and grassy and certainly far from the stinkiest thing produced on a farm (I’d vote for rotting potatoes). You can’t smell the methane, which is odorless.

Scientists estimate that 80% to 95% of a cow’s enteric methane (enteric meaning related to the intestines) comes from the burps. The rest comes in a very small percentage from cow farts but mostly from the stuff that immediately follows it, manure.

But a fart versus burps mix-up is the least of the matter.

What irked Mitloehner the most about Burger King’s cow-fart fiasco is that joking about cow farts and accepting that cows are a big climate change problem, which he considers a false narrative, misses the most critical point: Cows have the potential to induce global cooling.

“Big things happen when you reduce enteric methane,” says Mitloehner.

This is probably news to many. Cows are popularly considered a global warming culprit. It didn’t help that in 2006, the United Nations Food and Agriculture Organization erroneously reported that livestock produced more greenhouse gas emissions than the entire transportation sector. Mitloehner debunked that claim in 2010, and the FAO authors later admitted to the mistake and corrected it in their future reports.

But the focus on cattle as a leading cause of global warming still persists, and this frustrates Mitloehner. Instead of constantly debunking the cow fart myth and pointing out that cattle don’t produce more emissions than vehicles, he’d much rather be working toward turning cattle into a climate change solution. This idea is more complex than the cow fart theory: It requires understanding how methane and carbon work differently to induce warming.

Methane is a potent greenhouse gas, no argument there. It’s 28 to 36 times better at warming the planet than carbon dioxide. But while both carbon dioxide and methane are greenhouse gases, they exist in the atmosphere in entirely different ways. Carbon dioxide stays in our atmosphere for 300 to potentially thousands of years. Methane doesn’t: Approximately 95% of it breaks down in the atmosphere in about 10 years, with a small portion eventually converting to carbon dioxide.

Even though methane is more potent than carbon dioxide in the short term, it has a smaller cumulative effect on global warming simply because it doesn’t stay in the atmosphere nearly as long, said Myles Allen, PhD, a professor of geosystem science at Oxford University on the “Farm Gate” podcast in January. Allen, who’s also the coordinating lead author on the Intergovernmental Panel on Climate Change (IPCC) Special Report, argues that, for a ton of methane to reach the same thousand-plus-years warming effect as one ton of carbon dioxide, the rate of methane emissions would have to increase significantly and effectively be maintained forever. In a recent comment to the European Commission, Allen warned that miscalculating the effect of methane emissions “could mean eliminating practices, such as ruminant agriculture, that are not actually causing global warming.”

The other key pillar of Mitloehner’s idea is that the origin of a greenhouse gas makes a difference in how it builds up over time.

Burning fossil fuels releases vast amounts of carbon dioxide that has been locked up in the ground for millions of years, a “one-way street” direct to the atmosphere. But that’s not the case with ruminant-produced methane. Cows, Mitloehner explains, burp out the same greenhouse gases they consume. In other words, it’s “recycled.”

The recycling process starts with photosynthesis: Plants extract carbon dioxide from the atmosphere, storing some of it as carbon in their roots and leaves, perspiring some of it out at night, and (if ruminants don’t eat them) releasing the rest when they decompose. Cattle eat these plants and the carbon inside them. Then, they use a portion of that carbon for energy and to produce meat and milk. The rest of it is transformed, in the cow’s rumen, to enteric methane. Most of that methane gets burped up into the atmosphere where it hangs out for 10 years or so, until it is transformed back into carbon dioxide.

Plants continue to extract and store carbon dioxide. Cows continue to eat plants. Rinse and repeat — a cycle that has been going on for as long as ruminant animals have walked the Earth.

It’s when we optimize this process, aiming for efficient livestock production plus using new techniques to reduce enteric emissions, that the real magic — and potential for global cooling — is possible, Mitloehner says.

But wait a minute: Isn’t the problem that there are too many cows because of industrialized beef and dairy production? The FAO’s current report shows that global cattle emissions have increased significantly over the last 60 years.

All told, total emissions contributed by global livestock herds — cattle, chickens, pigs, buffalo, small ruminants, and other poultry — make up about 14.5% of current global greenhouse gas emissions. Cattle are the biggest contributors, producing about 62% of the total. So, it’s not like they get a free pass.

But, Mitloehner points out, you can’t ignore that the amount of food produced per cow varies immensely by country and that affects global cattle emissions. Less productive cows mean you need more cows for the same amount of food produced, hence higher emissions per pound of food. In the United States, beef cattle numbers have been dropping since 1975, and dairy herds are the lowest they’ve been in 100 years, a result of increasing efficiencies in production. Cattle only contribute to 4% of U.S. total emissions, much less than overall global statistics.

But while herd sizes have historically dropped in developed nations, the total cattle population worldwide has risen steadily, reflecting growing herd sizes in other nations. There are now 1.4 billion cows worldwide, and global cattle herds have increased by 561 million head since 1961. (U.S. cattle herds decreased by 3.4 million over the same time period.)

Those growing numbers, says Mitloehner, reflect growing human populations that lack efficient animal health and husbandry practices, including feeding. Emissions from cows in India, Pakistan, and Bangladesh could be reduced by as much as 38% if this were improved, according to the FAO. South American countries, including Brazil, at the forefront of criticism for burning the Amazon to support growing cattle herds, could similarly reduce their emissions by as much as 30%. Improving livestock-raising practices alone, according to the FAO, “can reduce livestock emissions by 20 to 30 percent across all production systems.”

“Decreasing atmospheric carbon by decreasing biogenic methane will have a cooling effect, and that makes everybody’s head spin.”

Simply put, globally, we could be getting a lot more food for the burps. This is especially worrisome because many of the developing countries with the least efficient practices, like those in South Asia, are expected to more than double their total livestock numbers by 2030 to meet growing populations.

But it is in that looming cattle emissions crisis that Mitloehner sees the opportunity to achieve global cooling without sacrificing food security.

We know methane has a strong but short-lived effect on our atmosphere. So, reducing methane should also have a strong cooling effect, if we assume for a moment that total carbon emissions are zero. And we know that keeping cattle herd sizes stable prevents increased global warming. What if we could maintain, even reduce herd sizes, via better practices while increasing the amount of food the ruminant herds provide? Then, to sweeten the deal, what if feed additives could reduce the methane a single, highly efficient cow emits? Cows could effectively consume more carbon — transforming it into food products to support human life — than they release.

“Decreasing atmospheric carbon by decreasing biogenic methane will have a cooling effect,” Mitloenher says, “and that makes everybody’s head spin.”

That’s where lemongrass comes in.

Burger King, to be fair, was sniffing along the right path to reducing enteric methane emissions using feed additives. It just took a strange trip down the wrong, lemongrass-scented road.

Feed additives work by inhibiting methanogens — a class of methane-producing bacteria — in the rumen, subsequently reducing the amount of methane that comes out.

The Burger King claim that lemongrass can reduce methane from cows by 33% was from a study conducted by the Autonomous University at the State of Mexico that has yet to be peer reviewed. Ermias Kebreab, PhD, associate dean for global engagement at the College of Agricultural and Environmental Sciences at UC Davis and Mitloehner’s colleague, did a follow-up study but wasn’t able to corroborate the results. Kebreab’s study, also not yet published, found negligible impacts on methane emissions, Kebreab tells OneZero. The discrepancy appears to be to be the result of lemongrass sourced from different areas: Lemongrass harvested from tropical and sub-tropical climates produces different compounds than lemongrass grown in temperate climates. UC Davis plans to repeat the lemongrass study with a tropically sourced lemongrass, Kebreab says.

But even pending a new study, Mitloehner, who did not directly work on the lemongrass study, is doubtful that it holds such significant potential. “I don’t think any of us believes that 33% is achievable with lemongrass,” he says.

Other feed additives, however, do hold that potential, or even more, and they’re much closer to FDA approval for use in the U.S than lemongrass, says Kebreab. Red seaweed, which was shown to reduce enteric methane by a whopping 80% in an early study, is particularly promising.

Kebreab just finished reviewing the current body of scientific literature on 90 potential feed additives. (Lemongrass wasn’t included because those studies are not complete.) He found plenty showing solid promise in reducing enteric methane. “We expect in the next two to five years that there will be some solutions that will help us get 30% to 50% reductions in (enteric methane) emissions,” Kebreab says.

After being racked through the coals on social media by Mitloehner, the Farm Babe (a popular Iowa farmer and farming myth-buster), and pretty much every agricultural and livestock group and farm proponent around, Burger King reversed course. They pulled the ad from TV a week after going live and asked Mitloehner, Kebreab, and colleagues for guidance going forward, according to AgWeb.

“Our Cows Menu campaign is just the beginning of an important journey focused on sustainability,” Fernando Machado, Burger King’s Head of Marketing, tells OneZero. “It is part of our ongoing commitment to help address the environmental impact of beef and educate the general public on this topic. We’re proud to partner with UC Davis’ Ermias Kebreab and Frank Mitloehner to expand on the results.”

Still, watching that video was a jaw-dropping moment for this former dairy kid. Now, there’s a new joke in my household: “Hey, um, maybe you could use some lemongrass?”

All fart jokes aside, Mitloehner’s idea could encourage many Americans that have bought into plant-based diets as a climate change solution to rethink their food choices from a global climate perspective. It’s easy to declare “Meatless Monday!” and feel better about climate change. But never mind that a 2017 PNAS study suggested that cutting out all animal protein — not just cows — from U.S. agriculture would only reduce the country’s greenhouse gas emissions by 2.6% (and make the U.S. diet critically nutritionally deficient).

Making climate-smart food choices means stepping away from narrowly framed arguments and getting a holistic picture of not only the pluses and minuses of our current food system, but also what might happen when we change it. We can’t talk about the impact of livestock on climate change without considering the economic and food security issues that go hand-in-hand.


It’s true that raising cattle requires land, and lots of it. Critics argue that it takes fewer resources to grow plant-based food than animals. But not all land is suitable for vegetable, fruit, nuts and grain production. Meanwhile, most farmlands (60%, according to the FAO) are best suited for use by cows and other ruminants, which can sequester carbon if managed correctly. In a life cycle assessment of his regeneratively grown beef (cattle raised using intensive grazing management practices), Georgia cattle rancher Will Harris discovered that the cattle on his 3,200-acre ranch sequester enough carbon in the soil to offset the methane emissions for his entire farm operations.

Emissions and nitrate pollution from manure can also be a problem, especially in dairy cattle. These are a major area for improvement for developed nations outside of reducing burp-produced methane. But with new technology, manure emissions can also be captured and turned into renewable biogas, and nitrate can be managed by filtering and recycling manure into reusable water, manageable fertilizers, and other products, like cow-manure fiber turned into packaging.

And eliminating cows doesn’t do anything to decrease the fossil-fuel emissions of diesel-fueled tractors plowing up land to plant and harvest crops.

Meanwhile, as the FAO notes, hundreds of millions of vulnerable people in developing countries will increasingly rely on livestock for their livelihoods as the planet warms. Animals, unlike many plants, are better adapted to withstand climate shock.

None of this means we should be eating more meat, especially in nations where we already have plenty of it. Mitloehner is very clear himself that cattle’s potential contribution to climate cooling only works if we avoid increasing herd sizes on a global level. It also doesn’t mean we shouldn’t keep looking for other solutions in the big picture, like vertical agriculture in urban areas and upcycling the 31% of U.S. food we leave to rot, which contributes 18% of the total emissions produced by landfills. It’s complicated, and there is no one magic pill for the perfect, climate-friendly food production system, be it derived from plants, animals, or some of both.

But it’s past time for the debate to shift away from the simplistic “cows are bad” narrative. That’s not a solution — it’s just a scapegoat with an udder. Getting rid of cows is just a trade-off for other problems that jeopardize food security while ignoring the giant, emissions-producing white elephant in the room: the burning of fossil fuels.

Instead, when it comes to cows, let’s understand and correctly measure methane’s impact on our environment to avoid chasing a false solution. Then, let’s implement husbandry, animal welfare, and efficiency practices that produce the food a growing and warming world needs while not increasing herd sizes. And, finally, rather than ignore and make fun of the science, let’s embrace new solutions, like feed additives, that can actually help cattle to feed the world while producing less emissions than they consume.

Or, as they say back home on the ranch, more feed additives, less farts. Ahem, burps.

Farmer. Writer. Journalist. Farm life, food & ag. Email at Follow at Open for assignments.

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