Future of the Environment

Study shows that feeding cows seaweed could help reduce methane emissions

image of cows in a field

Livestock produces large quantities of methane. Image: Unsplash/Ryan Storrier

Ermias Kebreab
Associate Dean and Professor of Animal Science, Director, World Food Center, University of California, Davis
Breanna Roque
Ph.D. Student in Animal Biology, University of California, Davis
Our Impact
What's the World Economic Forum doing to accelerate action on Future of the Environment?
The Big Picture
Explore and monitor how Future of the Environment is affecting economies, industries and global issues
A hand holding a looking glass by a lake
Crowdsource Innovation
Get involved with our crowdsourced digital platform to deliver impact at scale
Stay up to date:

Future of the Environment

  • Methane is the second-largest contributor to climate change and the majority of methane emissions caused by human activity comes from livestock.
  • Studies show that feeding cows seaweed supplements helps to reduce their methane emissions.
  • However, commercializing seaweed as a cattle food additive involves many steps and would need to be approved by regulators.

Methane is a short-lived but powerful greenhouse gas and the second-largest contributor to climate change after carbon dioxide. And the majority of human-induced methane emissions comes from livestock.

About 70% of agricultural methane comes from enteric fermentation – chemical reactions in the stomachs of cows and other grazing animals as they break down plants. The animals burp out most of this methane and pass the rest as flatulence.

There are roughly 1 billion cattle around the world, so reducing enteric methane is an effective way to reduce overall methane emissions. But most options for doing so, such as changing cows’ diets to more digestible feed or adding more fat, are not cost-effective. A 2015 study suggested that using seaweed as an additive to cattle’s normal feed could reduce methane production, but this research was done in a laboratory, not in live animals.

Have you read?

We study sustainable agriculture, focusing on livestock. In a newly published study, we show that using red seaweed (Asparagopsis) as a feed supplement can reduce both methane emissions and feed costs without affecting meat quality. If these findings can be scaled up and commercialized, they could transform cattle production into a more economically and environmentally sustainable industry.

Plant-digesting machines

Ruminant animals, such as cows, sheep and goats, can digest plant material that is indigestible for humans and animals with simple stomachs, such as pigs and chickens. This unique ability stems from ruminants’ four-compartment stomachs – particularly the rumen compartment, which contains a host of different microbes that ferment feed and break it down into nutrients.

This process also generates byproducts that the cow’s body does not take up, such as carbon dioxide and hydrogen. Methane-producing microbes, called methanogens, use these compounds to form methane, which the cow’s body expels.

We first analyzed this problem in a 2019 study, the first such research that was conducted in cattle rather than in a laboratory. In that work, we showed that supplementing dairy cows’ feed with about 10 ounces of seaweed a day reduced methane emissions by up to 67%. However, the cattle that ate this relatively large quantity of seaweed consumed less feed. This reduced their milk production – a clear drawback for dairy farmers.

Our new study sought to answer several questions that would be important to farmers considering whether to use seaweed supplements in their cattle. We wanted to know whether the seaweed was stable when stored for up to three years; whether microbes that produce methane in cows’ stomachs could adapt to the seaweed, making it ineffective; and whether the type of diet that the cows ate changed the seaweed’s effectiveness in reducing methane emissions. And we used less seaweed than in our 2019 study.

image of a steer eating alfalfa pellets as equipment measures his gas emissions
A steer eating alfalfa pellets as equipment measures his gas emissions. Image: Breanna Roque, CC BY-ND

Better growth with less feed

For the study, we added 1.5 to 3 ounces of seaweed per animal daily to 21 beef cows’ food for 21 weeks. As with most new ingredients in cattle diets, it took some time for the animals to get used to the taste of seaweed, but they became accustomed to it within a few weeks.

image of a cow eating food supplements containing seaweed
The cows who were being studied adjusted quickly to the seaweed in their diet. Image: Breanna Roque, CC BY-ND

As we expected, the steers released a lot more hydrogen – up to 750% more, mostly from their mouths – as their systems produced less methane. Hydrogen has minimal impact on the environment. Seaweed supplements did not affect the animals’ carbon dioxide emissions.

We also found that seaweed that had been stored in a freezer for three years maintained its effectiveness, and that microbes in the cows’ digestive systems did not adapt to the seaweed in ways that neutralized its effects.

We fed each of the animals three different diets during the experiment. These rations contained varying amounts of dried grasses, such as alfalfa and wheat hay, which are referred to as forage. Cattle may also consume fresh grass, grains, molasses and byproducts such as almond hull and cotton seed.

Methane production in the rumen increases with rising levels of forage in cows’ diet, so we wanted to see whether forage levels also affected how well seaweed reduced overall methane formation. Methane emissions from cattle on high-forage diets decreased by 33% to 52%, depending on how much seaweed they consumed. Emissions from cattle fed low-forage diets fell by 70% to 80%. This difference may reflect lower levels of an enzyme that is involved in producing methane in the guts of cattle-fed low-fiber diets.

One important finding was that the steers in our study converted feed to body weight up to 20% more efficiently than cattle on a conventional diet. This benefit could reduce production costs for farmers, since they would need to buy less feed. For example, we calculate that a producer finishing 1,000 head of beef cattle – that is, feeding them a high-energy diet to grow and add muscle – could reduce feed costs by US$40,320 to $87,320 depending on how much seaweed the cattle consumed.

a map highlighting the global sources of methane
Global sources of methane emissions. Image: Jackson et al., 2020, CC BY

We don’t know for certain why feeding cattle seaweed supplements helped them convert more of their diet to weight gain. However, previous research has suggested that some rumen microorganisms can use hydrogen that is no longer going into methane production to generate energy-dense nutrients that the cow can then use for added growth.

When a panel of consumers sampled meat from cattle raised in our study, they did not detect any difference in tenderness, juiciness or flavor between meat from cattle that consumed seaweed and others that did not.

Commercializing seaweed as a cattle feed additive would involve many steps. First, scientists would need to develop aquaculture techniques for producing seaweed on a large scale, either in the ocean or in tanks on land. And the U.S. Food and Drug Administration would have to approve using seaweed as a feed supplement for commercial cattle.

Farmers and ranchers could also earn money for reducing their cattle’s emissions. Climate scientists would have to provide guidance on quantifying, monitoring and verifying methane emission reductions from cattle. Such rules could allow cattle farmers to earn credits from carbon offset programs around the world.

Don't miss any update on this topic

Create a free account and access your personalized content collection with our latest publications and analyses.

Sign up for free

License and Republishing

World Economic Forum articles may be republished in accordance with the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License, and in accordance with our Terms of Use.

The views expressed in this article are those of the author alone and not the World Economic Forum.

Related topics:
Future of the EnvironmentClimate ChangeAgriculture, Food and Beverage
World Economic Forum logo
Global Agenda

The Agenda Weekly

A weekly update of the most important issues driving the global agenda

Subscribe today

You can unsubscribe at any time using the link in our emails. For more details, review our privacy policy.

1 in 5 migratory species are at risk of extinction, says a new UN report

Simon Torkington

February 21, 2024

About Us



Partners & Members

  • Join Us

Language Editions

Privacy Policy & Terms of Service

© 2024 World Economic Forum