How to Reduce Methane Emissions | Could Seaweed Animal Feed Be The Answer?

The average dairy cow quietly burps out 380 pounds of methane a year. Could we change what we feed our cattle to help keep their burps at bay and reduce methane emissions?

Methane is short-lived in our atmosphere compared to carbon dioxide, but it’s far stronger at warming our planet. Over a 20-year period, methane can trap 84 times more heat than the same amount of carbon dioxide.¹ 

Altogether the burps (and, to a lesser degree,  farts) of ruminant livestock are responsible for 30% of global methane emissions, or the equivalent of about 5.5% of all greenhouse gas emissions from human activities.²  So if we’re looking to prevent climate change, we need to somehow reduce the amount of methane cows are belching out.

Methane from cows starts with their food

Methane burps are caused by how ruminants digest their food. Ruminants have vast hidden communities of microorganisms living inside their gut, which break down and ferment the passing stream of plant mush that these animals spend their days chewing. These microbes form methane gas as a by-product, which is then released into our atmosphere mainly when the animal burps.

It seems that one way farmers could reduce the amount of methane ruminants burp out is to change what they feed their animals.¹ In a few studies, scientists found sheep burped out 80% less methane when they were fed 3% seaweed over 72 days, while beef cattle fed just 0.2% seaweed over three months burped out up to 98% less methane.⁴

Infographic by: Sachi Mulkey

Why does eating seaweed animal feed stop methane burps?

The seaweed of interest is a red tropical species called Asparagopsis, which is notably high in a substance called bromoform. Bromoform disrupts an enzyme used by certain gut microbes to produce methane, and so when eaten, it inhibits the microbial processes that produce methane in the stomach of ruminants.

Seaweed animal feed isn’t the only livestock feed that affects methane burps. Other experiments have shown ruminants burp out less methane when fed citrus and garlic, specific synthesized chemicals and more.⁵ The key is influencing the microbial community (the gut microbiome) inside the animal by inhibiting the microbial processes that produce methane or by reducing the population sizes of the gassiest species of bacteria.

Should we switch cows onto seaweed animal feed to help reduce methane emissions?

Seaweed animal feed is a new technology, with only a handful of studies completed so far and the first in-vivo studies (where seaweed is actually fed to real animals) only beginning in the past few years. So like any new technology, there are a lot of unanswered questions that research needs to address before we can get excited about using seaweed as a food for livestock.

Issue 1: How To Grow Enough Seaweed?

With nearly 1.5 billion cattle worldwide, sustainably growing and harvesting enough seaweed to feed them all would be a serious challenge.

Much of this seaweed would need to be farmed - and in huge quantities. The most economical way to do so would be to grow it in the ocean, but we would need to address some answered questions. Can we ensure that farmed seaweed remains high in bromoform and low in unwanted minerals? Plus, Asparagopsis needs subtropical waters to grow in, so what would the carbon footprint be of flying it from tropical ocean farms to cattle herds worldwide? Would it cancel out the benefits of low-methane burps?

Read more about seaweed farms.

Issue 2: Will Gut Bacteria Adapt to Seaweed in Animal Feed?

A ruminant’s gut microbiome is made up of many species of bacteria and other microorganisms called archaea, and scientists are still trying to understand how this microbial world works. If this delicate gut ecosystem is disrupted by a new feed, how long will the changes last before microbes adapt? Should additives like seaweed be included in rotation with regular feed or in combination with other methane inhibitors? 

More questions arise from the fact that no two animals are identical. The gut microbiome of each animal is unique, affected by its breed and where in the world it lives - so we don’t yet know whether seaweed feed will work in the same way across the billions of livestock scattered all across the world.

Further research will also need to make sure that altering the microbiome of ruminants to reduce their methane output does not have any unexpected ill effects on the health and well-being of the animal itself.

Issue 3: Does Seaweed Animal Feed Leave a Bad Taste?

If fed to animals long-term, will seaweed affect the taste of milk and meat? Currently, we don’t know, and only panels of human tasters will be able to answer that question. 

Meat and milk might also need to be monitored and possibly processed to ensure their safety, as compounds and minerals from seaweed could build up to levels that present a danger to humans - though studies haven’t yet found any evidence of adverse levels of bromoform in milk from cows fed with seaweed.⁶

Is seaweed animal feed the future of livestock farming?

Producing methane uses up about 2-12% of the energy available in the food ruminants eat.² In theory, if they are producing less methane, animals will have more energy to direct elsewhere - such as growing larger or producing more milk. But there are not yet enough long-term studies to convincingly indicate that lower methane emissions result in greater productivity in livestock farming in general. There are even fewer involving seaweed feed specifically,⁷ and those that do exist don’t always come to the same conclusions.

For example, one study showed beef cattle fed just 0.2% seaweed showed a 42% weight gain improvement and also burped out 98% less methane.⁴ But another study found the maximum reduction in methane production by dairy cattle was only 60%, which required a diet of 1% seaweed, and these dairy cattle also ate less food and produced 11% less milk than their traditionally-fed counterparts.⁸ Did cattle eat less because they saved more energy? Or did they dislike the taste? 

It’s vital to farmers that a new feed doesn’t cause animals any harm, to lose weight, or become less productive, so it’s important to fully understand the effect of seaweed feed on cattle before heralding it as a sustainable solution. So far studies look promising, but it’s too early to celebrate: first, scientists need to study seaweed and livestock much more, and over a longer period of time, in order to answer these outstanding questions.