By Conor McCabe

Cattle are special animals that consume foods such as grasses and hays that humans can’t digest, taking those pieces of energy and turning them into milk and meat that nourish people. In the process, part of the energy cows eat results in the production of methane that is belched out the front end of the animal. That’s a conundrum.

Methane is a powerful greenhouse gas that does impact our climate, and that is one reason there are groups that do not like beef and dairy production. However, methane is also a short-lived gas, meaning it lasts and warms the atmosphere for about a decade before being broken down into carbon dioxide and water vapor. This carbon is then available to be utilized by plants for photosynthesis to grow and produce oxygen, as part of the stockpile of CO₂ in the atmosphere.

The path of methane from cows to the atmosphere to plants and back to cows is known as the biogenic carbon cycle. This cycle is in constant rotation with methane molecules being produced, oxidized to carbon dioxide, and subsequently taken up by plants. In other words, as new methane is added, older methane is being removed at the same rate. However, if we have less methane produced today compared to a decade ago, we will have less going into the atmosphere and more of those historical emissions being removed.

That’s a major opportunity in the struggle to curtail global warming. As a result, the CLEAR Center and many other research centers around the world are working on solutions to reduce methane production in cattle without compromising animal health and performance.

Methane Emissions Start in the Cattle Stomach

Monogastric organisms have a single-chamber stomach. Dogs, pigs, cats – and people – are monogastrics. Conversely, cattle belong to a specific group of animals known as ruminants. Other animals in this category are deer, sheep, elk, buffalo, and antelope, among others. All of them evolved to have a ruminant stomach, a four-chambered organ that allows them to eat high-fiber foods such as grass and hay. Historically, it was an advantage for these animals to be able to rapidly eat a large meal of grasses and forage in a brief period and then digest it by rechewing it under the protection of cover.

The first chamber of the ruminant stomach, the rumen, is by far the largest one of the four, making up over 80% of the total volume. This compartment has an anaerobic fermentative environment, which means it digests food without oxygen. This condition allows trillions of microbes to grow, and they in turn help the cow or other ruminant animal break down grasses and other food inedible by humans into nutrients the animal can use.

In the process, this digestion pattern produces several free hydrogen (H⁺) and carbon dioxide (CO₂) molecules. One member of the rumen microbes are the methanogens. Although they account for only 1% of the microbes, they tend to get the most attention. These methane-forming microbes combine the hydrogen and carbon dioxide molecules in the rumen to form enteric methane (CH₄). Cows and other ruminant animals expel the methane via belching, at which point it enters the atmosphere and begins adding heat. 

But back to the cows’ specialized stomachs. It’s worth asking why they form methane and don’t use the hydrogen and carbon atoms for something else. It’s because this reaction uses the least energy possible and the body must get rid of excess free hydrogen molecules. Too many of these molecules can lead to a drop in rumen pH and rumen acidosis, which has negative implications for animal health and production. Methane formation acts as a makeshift drain, which can remove some of these hydrogen molecules and prevent the negative health outcomes from occurring.

The challenge with nature’s intricate system of ruminant digestion is that multiplying methane formation across all ruminants in the world amounts to a lot of methane — 109 million metric tons as of 2021 (FAOSTAT, 2024). More to the point, it affects global warming, which has implications for our climate. However, promising research shows that it’s possible to reduce methane production with minimal impact on animal health and production. The following discussions cover opportunities to reduce methane emissions from the most readily available to those that are the furthest away from incorporation into beef and dairy operations.

Changing cattle diets to reduce methane emissions

Changing what we feed cows in the United States can prevent some methane from forming in the first place, thus reducing emissions. One of the precursors for making methane is fiber digestion, and fiber is a key component of what cattle eat. Feeding cows grains and fats, for example, results in reduced methane formation. These food sources produce different digestion products during rumen fermentation. In fact, the products they make serve as a sink for some of the extra hydrogen molecules in a cow’s rumen. As a result, hydrogen is soaked up and can’t be used by the methane-forming microbes.

A prime example of this can be seen when comparing beef cattle that graze pastures and those feeding on 70% grain diets in feedlots. While feedlot cattle may be consuming more feed per day than cattle in a pasture, they are producing less methane for every pound of feed they consume. 

Indeed, feeding grains to cattle is a proven strategy to reduce methane emissions. However, there are also implications of livestock eating human-consumable foods such as corn and barley. There are tradeoffs that occur in each part of the livestock supply chain that carry their own pros and cons. Yet, most (86%) of what livestock eat cannot be consumed by humans, including feeds such as food byproducts, grasses and hays that can be upcycled into human-consumable food. Not to mention if these feeds are not consumed by livestock, they will head to landfills, where they surely will be producing methane as they decompose in anaerobic conditions.

There are well-known opportunities for producers to reduce cattle methane by modifying the current diets of their herds, but these strategies aren’t enough to achieve the reductions in methane emissions that are needed to meet current climate goals. Not to mention that the majority of the world's cattle are not fed a controlled diet every day, which makes It challenging to use this as a management strategy.

Using Genetic Selection for Lower Methane Emissions

Selective breeding allows livestock breeders to select favorable traits that produce healthier, more productive animals. There is an entire field of animal science that focuses on the heritability of certain traits. In other words, how likely it is that traits will be passed from parents to offspring. Some traits are more heritable than others and can be easily predicted. However, some have a lower predictability; it’s more difficult to say whether or not they will be passed to the next generation.

A relatively new area of research shows cattle living on the same farm can produce different amounts of methane. This is the same as cows that eat identical amounts of feed but produce unequal quantities of milk. The explanation for these varying outcomes seems to lie in the genetic factors that influence cows’ traits. 

Research demonstrates that genes related to methane emissions have low to average heritability. Although we need to do more work in this area – for example, genetically testing 10s of thousands of offspring from bulls to see how accurately we can predict heritability of low-methane-emission traits – it may be possible to reduce methane emissions by breeding cows with bulls that produce lower-methane-producing offspring. It is likely that before the end of the decade, bulls, along with being tested for their transmissibility of milk production and animal health traits, will also have a known level of methane-emissions transmission.

A Small Amount of Feed Additives Can Dramatically Reduce Methane

Feed additives include everything that makes up a minor, non-nutritional portion of the diet (<1%), with profound impacts on animal health, production and well-being. Think of additives as spices in terms of the amount of them that are added to the diet. Eating them alone would be too powerful but adding them as a dash on top of the feed helps make the meal complete. Historically, feed additives have been used to promote gut health and help cattle improve digestion via the use of enzymes.

More recently, we have developed feed additives to interrupt the methane-formation process and thus, reduce methane emissions. There are several methane-reducing feed additives; two of the most promising are 3-NOP (Bovaer) and bromoform [red seaweed (Asparagopsis taxiformis)]. Each of these feed additives stops the enzymes that form methane. 

Reducing methane emissions is of prime importance, but it is far from the only consideration. Animal health and production must also be weighed. Some feed additives check all the boxes, while others need further work before they can be recommended for the entire U.S. dairy or beef herd. Research has come a long way in finding feed additives that work to reduce methane emissions in research settings. However, the next frontier of feed-additive research will evaluate the consistent expected reductions in methane by implementing these feed additives in production settings.

At this point, there are no methane-reducing additives available on the market; they have not yet gone through a review and safety evaluation by the Food and Drug Administration. However, it is likely we will have approved options available as soon as later this year.

Capturing the Methane Before It Enters the Air

It isn’t possible to reduce a cow’s enteric methane emissions to absolute zero per day, even with the most powerful of methane-reducing feed additives. But what if we could capture the methane that the cows belch out, and store it or change it into something that doesn’t warm the planet as intensely?

That idea is currently being discussed by several startups that are fitting masks over the noses of cows, collecting burps as they’re expelled. The mask is equipped with a catalyst that oxidizes the methane into carbon dioxide and water. This process happens naturally in the atmosphere in about a decade’s time, but by oxidizing methane into carbon dioxide from the start, we can avoid 10 years of warming by atmospheric methane.

Masks aren’t the only devices being considered. Another system involves equipping cows with tubes near their mouths, which lead to methane storage containers in backpacks. The tubes act like a vacuum, sucking up all the methane that’s burped out and storing it on their backs. In addition to being kept from the atmosphere, the methane can be used as a fuel source.

This technique has been used in research settings for years via the Sulfur Hexafluoride (SF6) technique, where cattle are equipped with negative pressure yokes on their necks. Whenever they belch methane, a device at the level of their nostrils collects the methane and stores it for a 24-hour period in a yoke made from PVC. However, labor concerns quickly arise when it’s time to collect the methane, exchange it out for an empty container or perform routine maintenance. This is especially true with a large herd of cows. 

There are possibilities for methane reducing vaccines

One of the most exciting potential methods of inhibiting methane production is vaccination. When cattle and humans are vaccinated, their immune systems produce specific antibodies that attack and fight the pathogen of interest. A different vaccination is needed for every target because these antigens are specialized and only work against the target cell/pathogen of interest.

The same concept is being applied to the methanogens that reside in the rumen, with the goal of developing a vaccination would cause cattle to produce a specific antibody in their saliva. Since cows consume several meals throughout a day and are constantly rechewing their food and swallowing it, they produce gallons upon gallons of spit every day. The antibodies produced in their saliva would find their way to the rumen, where they would interfere with methane formation by the methanogens. Although it is promising, this technology is still going through the development phase and is unlikely to be available before the end of the decade. Clinical trials, on-farm testing and regulatory approval are needed before farms can use this technology. Further, there is no guarantee vaccinations will work for all production settings.

There is No Silver Bullet Against Methane 

Cattle naturally produce methane daily due to the special stomachs they have, which allow them to consume high-fiber feeds. As far as global warming is concerned, it’s a major consideration. In fact, we won’t be able to use one technology or solution to solve an issue as big as enteric methane emissions from cattle production. In an ideal world we want to find solutions that are easy to implement and reduce the greatest amount of methane. Given feed additive's strong methane emission reductions and ease to be added to a farm, it has received the most attention. However, feed additives won't be our end all be all as there are solutions needed across the supply chain to achieve the emission reductions we need to make an Impact for climate. 

It’s worth researching the effect of concurrent use of multiple technologies (e.g., feed additives, genetic selection, and diet formulation). Would there be a greater reduction or the same impact in reducing methane emissions compared to one of these technologies alone? Animal scientists are confident about how diet can interact with the amount of methane produced, but with products that aren’t available outside of a research setting (feed additives/vaccines), the impact on methane emissions in production settings is presently unknown. 

With large climate goals to drastically decrease global methane emissions, reducing cattle burps is necessary to achieve these commitments. To make this happen, it will take the right combination of the above technologies, management decisions and collaborations to help producers drive down emissions and continue to shrink the sector’s environmental impact.