Chew on this: Fighting climate change by reducing cow burps

Featured image from

Roque BM, Brooke CG, Ladau J, Polley T, Marsh LJ, Najafi N, Pandey P, Singh L, Kinley R, Salwen JK, Eloe-Fadrosh E, Kebeab E, Hess M. 2019. Effect of macroalagae Asparagopsis taxiformis on methane production and rumen microbiome assemblage. Animal Microbiome 1: 3.


If you have studied climate change, you might know that the ocean is often referred to as a “carbon sink”, meaning it can capture and store excess carbon that is emitted on land. One way this can occur is through the many things that grow in the ocean – for example, algae or seaweed take in CO2 to produce their own food. Now, scientists have started to wonder if there are other ways these photosynthetic organisms can help combat climate change and reduce greenhouse gases on land.

Cows are ruminant animals. They digest food through a process called “enteric fermentation”, which is how the food is broken down in the cow’s stomach (Figure 1). A by-product of enteric fermentation is methane. Essentially, the majority of methane released from a cow is through their burps. In the US, 25% of all methane emissions come from ruminant animals!


Figure 1. A diagram of cow digestion, illustrating how methane is produced by methanogens (a methane-producing bacterium) in the cow’s stomach. Image created by the author.


Asparagopsis taxiformis is a red macroalgae, what you would probably just call “seaweed”. Scientists in Australia have shown that by mixing this species of seaweed with hay in cow feed, they are able to reduce the methane emissions by dairy cows by up to 99%. It also provides important minerals and nutrients to the cows, and redirects the energy normally used to produce the methane molecules into producing proteins for the cow. This reduces the overall food requirements for the cows, making it a more sustainable feed in more ways than one.

Figure 2. Asparagopsis taxiformis, the seaweed used as cow feed in the study. Image from Wikipedia


Why Does This Matter?

A recent IPCC report, published by a group of scientists from around the world in October 2018, claimed that we have just 12 years left to address climate change. Although we are already seeing the effects of climate change in increasingly dangerous weather and species dying off, the 12 years is the time these scientists estimate that we have left to significantly reduce global carbon emissions, in order to have more than a 50 % chance of keeping global warming below 1.5°C (about 2.7°F). This means that we need to look for ways to drastically reduce carbon emissions on a huge scale.

Globally, livestock farming contributes approximately 27% of greenhouse gas emissions. Every dairy cow produce approximately 110 kg (242 pounds) of methane a year, equivalent to the amount produced by 74 pigs. Methane is the second most common greenhouse gas after CO2, but it has 28-34 times more global warming potential as CO2. If we can really reduce cow emissions by as much as this article claims, we could make a huge dent in our global CO2 emissions.


The Next Step

Although this is a really cool bit of information, and has the potential to cut out a huge chunk of carbon emissions, it is not a perfect solution.

There are currently 94.8 million cattle in the US, and each one of them needs to eat approximately 27 pounds of feed per day. Taking native seaweeds in the quantities these cows would need could harm natural ecosystems along our coasts. Currently, there is not enough seaweed farmed in America to feed all of the cows we have. Some areas that are potentially the most productive for future seaweed farming, like the coast of California, have many restrictions and complicated permitting procedures. It may take a while to be able to produce seaweed on the scale that would be necessary to feed all the cows we currently have in the United States.

Additionally, cow burps are not the only part of livestock farming that produces methane. In order to make farming more sustainable in the future, we need to reduce carbon emissions in transportation, manure storage, and other sectors of the care and keeping of dairy cows. Just something to consider the next time you reach for the cheese!


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Maddie Halloran

I am a second year master's student at Humboldt State University in the Fisheries Biology Department. I'm interested in human impacts on the environment and conservation. When I'm not counting fish you can probably find me outside on an adventure or eating ice cream on my porch.

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