Feeding Cows Seaweed Can Reduce Methane Emissions, but the Additives Still Come With Plenty of Challenges

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In the cold dark of 5 a.m., Kyle Moellar, an apprentice at Wolfe’s Neck Center for Agriculture and the Environment, ushers a herd of cows into the milking parlor. Each waits patiently for her turn to stand, eight at a time, in the milking stalls, her udders dipped in disinfectant before the suction cups are applied. Once milked, Kyle lays a hand on each of their backs and whispers “thank you mama” as he guides them out. Although these cows live a mostly traditional life, they’re also part of a cutting edge experiment with an unusual ingredient—local seaweed.

Wolfe’s Neck Center has around 40 milking cows and produces over 1,000 pounds of organic milk a day. Recently, it took part in a research trial with Bigelow Laboratory for Ocean Sciences in Boothbay, Maine to see if feeding seaweed to cows could reduce the methane they produce. Preliminary results have been positive but there are still some challenges to overcome including, crucially, how to make this profitable for dairy farmers. If those questions can be answered, this solution could not only dramatically reduce carbon emissions in the dairy industry, but also help to safeguard Maine’s coastal economy against the threat of warming waters.

Methane is a potent greenhouse gas with 80 times more warming power than carbon dioxide, over a 20-year period. It’s responsible for about 30 percent of the global warming we’re experiencing today, and agriculture is the largest human source of methane emissions. Within that, cows are the single biggest offenders—burping out methane as a byproduct of their digestion process.

The United Nations has stated that “cutting methane is the strongest lever we have to slow climate change over the next 25 years.” Similarly, climate researchers have warned that without cutting methane emissions from the meat and dairy industries, the Paris Agreement will fail.

Nichole Price, a senior research scientist and director of the Center for Seafood Solutions at Bigelow Laboratory for Ocean Sciences, has been working with a team of scientists for nearly a decade on a seaweed-based solution to reduce the methane that cows emit. Inspired by research from Australia, which showed that a tropical seaweed called Asparagopsis could significantly reduce a cow’s methane emissions, Price and her team started experimenting with seaweeds native to Maine in 2015. Unlike Asparagopsis, which requires warm waters and cultivation in land-based tanks that have their own environmental footprints, sugar kelp is the most commonly farmed seaweed in the U.S and can be grown with minimal impact. Pilot studies have shown promising results—up to 50 percent reductions in methane, according to Andre Brito, associate professor of dairy management at the University of New Hampshire, who collaborated with Price. While the exact numbers are not yet published, Price admits that “we’re excited, let’s just say that.”

Indigenous people across North America have used seaweed as a food, medicine and textile for centuries, but it’s only in the last 20 years that scientific interest in seaweed has really taken off. Multiple species of seaweed, including Asparagopsis and sugar kelp, produce a bioactive compound called bromoform that disrupts the methane-producing microbes in a cow’s digestive system, preventing production of the greenhouse gas. However, bromoform is a volatile compound that can easily escape from the seaweed during storage, making the seaweed less effective at reducing methane over time.

“Sometimes the seaweed was very effective,” says Brito, speaking about a recent study the team has not yet published, “then a couple of days later you’d see less response.”

Price and her team are researching ways to stabilize the bromoform and generate a more constant methane reduction in the rumen. “We’re working on making sure that whatever additives we come up with have a shelf stability,” she explains. “It’s the last challenge, and that’s exciting me.” Another animal trial with the University of New Hampshire is due to start this spring.

Price is also excited about possible policy advancements that could offer a new route to earn FDA certification for their product. Currently, a seaweed product would require drug certification, a long and expensive process requiring years of clinical trials. But new legislation called the Innovative FEED Act of 2023, currently under review by Congress, would allow seaweed to qualify as a gut-modifier, a classification with a less arduous approval process. Other countries, including the U.K., Canada, Australia, New Zealand and those in the EU, have had that certification for years.

“The United States is really behind, not only in seaweed production and marketing but in regulatory pathways,” says Price.

If approved, Bigelow’s product could open up a huge new market for Maine’s burgeoning seaweed industry. Despite a long history of wild seaweed harvesting, the U.S.’s first commercial kelp farm wasn’t established until 2009. That operation was opened by Atlantic Sea Farms (then called Ocean Approved) in Casco Bay, just 17 miles from Wolfe’s Neck Center. Working with small independent fishing partners up and down the coast to grow kelp in the winter months, it’s grown its output every year since it was founded.

Atlantic Sea Farms lowers the barrier to entry for farmers by providing the initial seeds and a buy-back guarantee that promises to take their harvest. Last year they produced a combined 1.3 million pounds of kelp. They’re expecting to double that in 2025.

“The level of scalability here is incredible,” says Thew Suskiewicz, their director of sea science. “Right now there’s only 120-130 acres being actively farmed out of several 100,000 potential acres.”

Their mission is driven by a need to diversify Maine’s marine resource harvesting economy, which generates over 75 percent of its revenue from lobster harvests.

“Having your entire coastal economy based on a single species is never a good idea,” says Suskiewicz. Warming waters have caused a total collapse of the lobster industries farther south, around Long Island and Massachusetts, and Suskiewicz has seen that pattern progress up the coast over the last 20 years.

“It’s complete destitution, people can’t keep their boats, people can’t keep their houses,” he says. “I have a six-year-old daughter, I want her to be able to grow up in coastal Maine.”

But it’s hard to grow an industry without a growing demand for the product. Although seaweed is the fastest growing aquaculture sector in the U.S., the nation’s production accounts for less than 0.1 percent of global supply, and pales in comparison to countries like South Korea, which has a seaweed industry that employs thousands and produces exports worth $750 million. With only 40 partner-farmers and 18 employees, Atlantic Sea Farms is the largest seaweed company in North America.

“Every single month we’re wondering, how much more kelp can we sell? How do we build this market?” says Suskiewicz. He’s hopeful that Price’s work will open up new opportunities.

The biggest challenge, however, will be making seaweed additives an attractive proposition for farmers.

“Even if it does work,” says Thomas Prohl, the senior manager of farm operations at Wolfe’s Neck Center, “one issue is the cost.” While organic dairy farmers are more in control of their margins than most—at Wolfe’s Neck they have grass-fed cows and a consistent buyer at Stonyfield Organic, which is owned by dairy giant Lactalis—for conventional dairy farmers, not only can the price of feeds like grain or alfalfa fluctuate due to world events, such as the war in Ukraine, but the sale price of milk “goes up and down like the stock market,” says Prohl.

Even if they wanted to, Prohl says, “there’s no money to give away if you’re a dairy farmer not making much.”

Research from the University of New Hampshire found that half of the organic dairy farmers surveyed in Maine would be willing to pay a little extra for a methane-reducing seaweed additive, but only if it qualified them for government subsidies or had additional benefits such as higher milk yields or health benefits for the cows that reduced veterinary bills. Whether sugar kelp can deliver such additional benefits is something Price is exploring, and will be the subject of future trials.

Another possible way to profit is by selling carbon credits for reducing methane. But that depends on the development of well-regulated carbon markets and accurately measured, verifiable reductions— something that Congress is making difficult. First though, farmers need to be able to measure the methane. The research trials at Wolfe’s Neck used an $80,000 ‘Green Feed System’ that sampled the cows’ breath as they ate—an investment out of most farmers’ reach. Price’s team has received a grant from the National Science Foundation to develop smaller, cheaper, wearable methane sensors for the cows. If they succeed it could be much easier for farmers to receive payments for reducing methane or credits that could be sold in a carbon trading marketplace.

Prohl has further concerns about the scalability of a seaweed additive, pointing out that not all dairy farms are near the coast, such as those out in the Midwest. Cows eat an average 40 pounds of food a day. Even though the seaweed required would be less than 1 percent of their diet, that’s still a huge quantity.

“Transporting it across the country has carbon emissions too,” he adds. “In my opinion, I don’t think it’s going to be the sort of thing that changes the dairy industry, especially considering the majority of those methane emissions are coming from farms with 3000-5000 cows, not 30-40.”

Price agrees that adding sugar kelp grown in Maine won’t work for everyone raising dairy cows, but she doesn’t see this as a “silver bullet, one-size-fits-all solution.” Her lab is also working on solutions with microalgae, also known as phytoplankton, which can be grown in vats of salty water on land. While it wouldn’t qualify as organic, it’s a cheaper option that could be grown locally in landlocked states. Bigelow Ocean Laboratory has almost 4,000 strains of microalgae in their repository, and Price’s team is testing them all.

“We’ve got some really strong candidates,” she says, “but we’re still screening across all of those options.”

However, for farms by the coast, there’s little doubt that a partnership that expands the kelp industry has other environmental benefits. Kelp forests absorb excess nitrogen and phosphorus in the water, cleaning up marine pollution. A study published in Nature found that each hectare of kelp forest provides habitat for an average of 900 kilograms of harvested fish and seafood annually.

Kelp’s high photosynthesis rate makes it potentially 20 times more effective at sequestering carbon than land plants, and when bits of seaweed fall to the ocean floor, that carbon is locked away in sediment long term. Farmed ocean kelp needs no fertilizer, pesticides or additional water. “It’s a zero-input crop,” says Suskiewicz. “It’s low impact, it’s scalable and it’s delicious.”

It’s still a long road, but Price is optimistic they can solve the hurdles, making kelp a profitable business proposition for both harvesters and dairies. “With aquaculturists and terrestrial farmers working together, we can offer new market opportunities for both and help meet climate emissions goals,” she says. “It’s a win-win-win.”