Joan Salwen has always had a thing for cattle. How could she not? She comes from a lineage of livestock farmers that stretches back to the American Revolution. Salwen grew up in southeastern Iowa, in the shadow of her grandfather’s farm in Mount Auburn. As a child, she was often tasked with helping her grandmother in the kitchen, organizing the pantry or preserving cherries from the orchard. But her favorite chore was helping her “Grandpa Mo” King release the livestock into the pasture at the end of the day, giving them free reign of the farm.

Mo King’s cattle would pick their way across the pasture, grazing on grass — the first step in their miraculous process of turning what is nutritionally useless to humans into the building blocks of life. The dairy and beef that cattle produce are packed with protein, feeding billions on the planet.

But there’s a catch, which Salwen was shocked to learn as an adult: the fermentation process in the stomachs of cattle means that they burp huge amounts of methane, a greenhouse gas that is 28 times more powerful than carbon dioxide at warming the planet. In fact, one highly productive dairy cow emits four metric tons of carbon per year — roughly the same as a passenger car. “If you could take every car in every country and put it in a garage forever, that would be equivalent to stopping the methane burps from all cows,” says Salwen.

While we are decades away from putting our cars away forever, Salwen, an Emerson Collective Dial Fellow, believes she has found a way to help farmers nearly eliminate the harmful methane emissions from cattle in the United States by the end of this decade. Her company, Blue Ocean Barns, is working to do just that, using an ingredient found underwater, thousands of miles from Mount Auburn, Iowa.

“I believe that farmers like my grandfather are model stewards for our planet,” Salwen says. “They just need the right tool to serve as heroes in slowing climate change.”

Eventually, Salwen’s family moved away from her grandfather’s farm, and Salwen began her professional career as a business consultant, helping financial-services companies launch new products. But her agricultural roots always beckoned. In 2016, she decided to start a new professional chapter, and entered Stanford University’s Distinguished Careers Institute for a year-long program, which she calls a “gap year for grown-ups.” She had one, very specific goal: to develop ways to help livestock farmers like her grandfather to stop climate-warming cow burps.

Late one night, burrowing into one of her routine internet rabbit holes, Salwen came across a 2016 research paper, published by Australian scientists, that described the methane-inhibiting effects of a hard-to-pronounce red seaweed, Asparagopsis, on the cow digestive system. The seaweed, which is abundant in many temperate and subtropical regions like Australia and Hawaii, can actually block carbon and hydrogen atoms from combining to form the harmful, greenhouse gas.

With $1 million that Salwen was able to raise, she enlisted the University of California, Davis, to study whether the methane-inhibiting effects of the seaweed were replicable and would persist in the cow digestive system over time.

After countless phone calls to Australia, Salwen got her hands on some dried Asparagopsis. (“It's not available from Amazon Prime,” she jokes.) The team studied the seaweed in beakers in the lab (“like you would see in a mad scientist movie”) and tested it on a robotic cow stomach. Early results were promising, so they began to feed the seaweed to a group of live cows. Soon, they knew that the supplement was safe for cattle and human consumption. Additional studies then proved that the seaweed led not only to a persistent reduction in methane emissions but also that the reductions had grown over time.

“That's when I really said, ‘Holy cow!’” Salwen remembers, “A lot of the things that we are going to have to do to arrest climate change are going to be really hard, but that is just not the case here. This seaweed is going to change the world.”

Today, Blue Ocean Barns, the company she co-founded with Matthew Rothe, is building the technology to grow vast amounts of Asparagopsis taxiformis on the Big Island of Hawaii, in San Diego, and other sites. It has designed a novel production system to aid in the growth process. More importantly, the company has unlocked the code for producing a variety of Asparagopsis taxiformis at a cost that will work for farmers.

Farmers need to add only a half-cup of the dried, Blue Ocean Barns seaweed into cows’ nutritious daily feed — which would represent less than 0.5% of their overall diet — to reduce their methane emissions by a staggering 80% or more.

“The light footprint and speed of this climate solution is almost unparalleled,” Salwen says, contrasting her seaweed supplement to time- and infrastructure-heavy climate solutions, like eliminating fossil fuels or updating the power grid. “The very first day that a cow eats this seaweed, she stops burping methane.”

To become a sustainable business, Blue Ocean Barns will need to start by teaming up with the world’s largest dairy producers. Salwen says that the time is ripe for her solution because many global food companies are setting aggressive sustainability goals that Blue Ocean Barns can help their farmers meet efficiently.

“The cow burps are the number one contributor to corporate greenhouse gas emissions for dairy companies,” she says. “Many of these companies are knocking themselves out to put solar on their buildings, or are transitioning their vehicles to renewable energy. But as long as the cow is standing there, burping away, they're just never going to make it.”

Salwen will also have to build trust with the farmers who provide the dairy to these food companies. After all, farmers are the only ones who can feed this supplement to cows. Livestock nutritionists have spent decades carefully calibrating diets for dairy cattle, and it won’t be easy to convince farmers to tweak those prized recipes.

Fortunately, Salwen reports, there’s a second benefit of Asparagopsis taxiformis that could help with uptake: by redirecting hydrogen during the digestion process, the supplement allows cattle to make better use of the feed they are already eating, improving energy availability and productivity — more beef and milk — for less feed. Salwen believes that additional research and farmer testimonials will make the case to dairy producers.

“Farmers have long been caring stewards of their lands, and our ingredient immediately equips them with a highly effective natural tool for caring for the climate,” she says. “When they choose to feed this to cows, farmers will be exhibiting a level of heroism that can be inspiring to all other industrial sectors in our country.”

There’s one important farmer who shares Salwen’s vision and ambition: Albert Straus, founder of the Straus Family Creamery in Marin, California, the first 100-percent certified organic creamery in the U.S.

In a pilot project recently approved by the California Department of Food and Agriculture, Blue Ocean Barns and Straus will begin working this Spring to prepare to feed the seaweed to the cows on Straus’ farm. If all goes as planned, dairy from climate-friendly cows will begin appearing on shelves in July anywhere that Straus Family Creamery products are sold.

“The project will be evidence to California dairymen, the dairy associations, and the regulators that this is a simple and effective solution — just cows eating feed, like they always do, and happily generating milk that tastes delicious,” Salwen says. She hopes that this pilot project will inspire broader adoption by the end of this year.

Thinking back to her own childhood in Iowa, Salwen says that she has no doubt that Grandpa Mo would have fed her seaweed supplement to his cattle. “No question. He would really, really love this,” she says. “If you said, ‘Feeding this to your cows will keep the earth safe and cool for your children and grandchildren,’ he’d be all in.”