How to Stop Farts From Warming the Planet: Feed Cows Seaweed
Talk about magic seaweed: A single type of red seaweed could cut greenhouse gas emissions, fight ocean acidification, remove invasive species, restore fisheries, and help coastal economies around the world.
Researchers in Australia have discovered that the seaweed, Asparagopsis taxiformis, when mixed into livestock feed in small amounts, reduced methane emissions from sheep by up to 80 percent.
Livestock emit methane mostly through burping, while farts and manure also contribute to the total. The animals are estimated to generate 44 percent of all human-related methane, which has up to 36 times the global warming potential of carbon dioxide.
For the last few years, scientists have explored the use of seaweed additives to reduce methane emissions from livestock, with only modest results. A study published last year found a 16 percent reduction using one type of seaweed.
But researchers at Australia’s Commonwealth Scientific and Industrial Research Organization and James Cook University have been conducting lab tests on a variety of seaweed species for their methane-reducing properties. When they tested Asparagopsis taxiformis, they were astonished.
“We thought our instruments were broken—the reduction rate was more than 99 percent,” said Michael Battaglia, CSIRO’s group leader on greenhouse gas mitigation and adaptation in agriculture. “It was virtually undetectable.”
When researchers gave the seaweed to sheep, at a ratio of just 3 percent of the feed, they found a methane reduction of up to 80 percent.
“Livestock burps and farts account for 5 percent of all global greenhouse gas emissions,” Battaglia said. “The total contribution from land transportation is 10 percent, so we’re talking about the equivalent of half of all the vehicles in the world. It’s not a trivial number.”
Asparagopsis taxiformis contains the compound bromoform, which reacts with vitamin B12 at the last step of digestion and disrupts enzymes used by gut bacteria to produce methane. More trials on sheep and cattle are under way, Battaglia said.
The question, then, is where would all that seaweed come from? The researchers estimated that some 23 square miles of seaweed farms would be needed to create enough additive for just 10 percent of all Australian livestock. Producing enough product for the 92 million cattle in the United States alone would require seaweed farming on an unprecedented scale.
But that might be a good thing.
Many seaweeds thrive in acidifying ocean waters, according to the U.S. National Oceanic and Atmospheric Administration. They absorb carbon dioxide and nutrients that contribute to ocean acidification while emitting oxygen that prevents formation of dead zones in the ocean.
“The combination may result in seaweed farms acting as protective ‘halos’ that mitigate acidification and pollution locally while creating habitat for marine species,” the agency states on its website.
NOAA runs an experimental seaweed farm in Washington state, in collaboration with the Puget Sound Restoration Fund, to assess its potential to mitigate acidification while also supplying a valuable ingredient for food, medicine, biofuel, and fertilizer.
“I was amazed by the information” out of Australia, said Jonathan Davis, senior scientist at the restoration fund. “I’m going to look at our own seaweed farm and see if there’s a potential to find a native species within the same genus and potentially grow it here in the Pacific Northwest to create a new crop for a commodity.”
Asparagopsis taxiformis is found in many parts of the world, though it is considered invasive in most of them. Turning it into a valuable commodity for the livestock industry, Davis said, would provide financial incentives to remove it from nonnative waters.
“I don’t see any downside to it,” Davis said. “Removing invasive species is always a good thing, especially if it has commercial value, and I would say there’s an opportunity to potentially make money.”
Battaglia agreed. “This is something that we can potentially tackle without causing any economic disruption,” he said. “We can try to make the transition to a lower-carbon economy while achieving benefits along the way.”
Those benefits include creating alternative livelihoods in developing countries where fishing is declining or communities are involved in destructive, unsustainable forms of fishing.
Could the idea catch on in the United States?
“We are certainly open and receptive to the idea of feeding cattle dried seaweed to reduce methane emissions and look forward to additional research on the topic,” Lia Biondo, a spokesperson for the United States Cattlemen’s Association, wrote in an email. “We take great care in sustainably managing our resources to ensure the long-term health of the land.”
Environmentalists had mixed reviews of the idea.
“This study presents another interesting option but also raises the important reminder that we need to think carefully about all of the possible benefits and unintended consequences whenever we consider a new solution,” Marcia DeLonge, an agroecologist at the Union of Concerned Scientists, wrote in an email.
“More agroecological research, which views farms as ecosystems embedded in landscapes and societies, is so urgently needed, especially for systems like beef production that currently have a big footprint,” DeLonge wrote.
Jonathan Kaplan, director of the Food and Agriculture Program at the National Resources Defense Council, cautioned that seaweed wouldn’t alleviate other environmental damage caused by livestock, including greenhouse gas emissions from fertilizer used to grow grain for livestock.
“While we pursue technology strategies like this, which are potentially very important, we also have to look at the larger equation and ask if we can really be sustainable with all the animals we’re creating and consuming,” Kaplan said, “and I think the answer is that we cannot.”