The Health and Environmental Benefits of Seaweed

• Seaweed is a versatile food that provides key minerals like iodine, magnesium and calcium.
• Adding seaweed extract to cattle feed could help reduce their methane emissions.
• Seaweed can also be turned into biodegradable plastic.

Agriculture is one of the pillars of modern society. While it allowed humans to transition from nomadic tribes to urban dwellers, modern farming and animal husbandry have come with a major drawback—large-scale agriculture is one of the leading drivers of climate change, accounting for about one-quarter of the world’s greenhouse gas emissions. But what if there was a solution that required no land or fresh water, provided a nutritious and delicious food source, and could even be turned into biodegradable plastics and manage methane emissions? It’s not too good to be true: it’s seaweed. 

What Makes Seaweed So Special? 

Seaweed, the edible algae that grows across oceans and bays, is a nutrient-dense plant that’s commonly eaten throughout Asian cultures. From the nori used to make sushi rolls to the kombu infused in umami-rich dashi, seaweed is an important component of a variety of dishes. Depending on the type, it can be crunchy or tender and salty or pungent. Plus, it’s also one of the few foods that has the potential to both remove carbon from the atmosphere and reduce greenhouse gas emissions.

“I grew up around the ocean, so I’ve seen firsthand how much pollution ends up there,” says Rand G. Packer, chef and founder at Evoke 1923, who is passionate about cooking with seaweed. “The ocean is resilient, but it will not always be that forgiving.” 

He sees seaweed as providing serious benefits, both for its potential to help relieve some effects of climate change as well as for its rich micronutrient profile. “Seaweed is nutrient-dense and adds flavor and texture to a dish that you cannot replicate with any other ingredient,” Packer says. 

Health Benefits of Seaweed 

Seaweed is high in micronutrients like magnesium, iron, calcium and vitamin K, explains Alexis Law, RDN. It also contains polyphenols, which can help reduce inflammation and the risk of heart disease, she says. She suggests enjoying seaweed in a salad or sprinkled on a bowl of salmon, rice and cucumbers for a boost of flavor and nutrition. 

But those aren’t all of the nutrients seaweed contains: “Seaweed can be a large contributor of iodine in the diet, which our body does not make on its own,” Law says. Iodine is crucial for metabolism and thyroid health, and is especially important for those who are pregnant.

How Does Seaweed Farming Benefit the Environment? 

Seaweed has a low carbon footprint, explains Rod Fujita, Ph.D., director of Ocean Innovations. Fujita, a leading marine and aquaculture researcher, says there are great opportunities for this algae to have a real impact on our carbon use. While he’s optimistic about the use of seaweed as part of the solution to reducing greenhouse gas emissions, Fujita notes that dietary changes won’t be the driving factor. That said, there are several other ways seaweed production can have a notable impact on the environment.

Carbon Sequestration

Fujita says there’s urgency to both reduce our greenhouse gas emissions and remove it from our atmosphere. Seaweed helps on both fronts. It absorbs carbon from the ocean, which can lower the water’s carbon concentration. This, in turn, allows the ocean to absorb more carbon from the atmosphere—a process known as carbon sequestration.

Still, the full carbon-capturing potential of seaweed depends on what happens after it’s grown. If the seaweed is eaten by fish or microbes, or if carbon leaks out during decomposition, some of the sequestered carbon will be re-released. Scaling up seaweed farming could amplify the environmental benefits over time, but the current impact is modest.

Alternative Fertilizers

One of the most exciting opportunities is using farmed seaweed in agriculture. It has the potential to help curb greenhouse gas emissions in cattle ranching, plus seaweed could be used to absorb pollution in our waterways and even limit future water pollution. 

Cattle are major methane emitters. But research shows that adding seaweed to their feed can significantly cut methane production. This is because seaweed contains bromoform, a compound that reduces methane in cows’ digestive systems. According to Fujita, this could make a major dent in emissions. However, excessive bromoform can be toxic to cattle, so more research is needed to determine safe and effective use.

Seaweed may also help tackle nutrient pollution in oceans. Runoff from farm fertilizers often carries nitrogen and phosphorus into the ocean, overloading waters with nutrients. Since seaweed naturally absorbs these compounds, it could play a role in cleaning up polluted waterways. In addition, seaweed can be processed into a nutrient-rich extract that promotes plant growth. By supplementing with seaweed extract, farmers may reduce their reliance on expensive synthetic fertilizers, which are a major source of water pollution. This shift could provide both agricultural and environmental benefits—and potentially save farmers money, too.

Bioplastics

Another promising innovation? Biodegradable plastic made from seaweed. Traditional petroleum-based plastics can take centuries to break down—and they never fully decompose, instead fragmenting into microplastics. There are roughly 6.9 billion tons of plastic waste on the planet. More than three-quarters of this is now in landfills, and the United Nations Environment Programme says that the equivalent of 2,000 garbage trucks full of plastic are dumped into the world’s oceans, rivers and lakes every day. That plastic waste alters ecosystems by destroying natural habitats like coral reefs and injuring or killing sea life. 

While Fujita says that while bioplastics are unlikely to completely replace petroleum-based ones, shifting the balance could significantly reduce greenhouse gas emissions in their production, disposal and incineration.

There are already companies turning seaweed into plastics. Take San Francisco-based Sway. They created a pellet made from seaweed that can be used to make practically anything that is made from plastic, and the packaging is compostable—at home or an industrial compost facility.

Tips for Adding Seaweed to Your Diet

Some of the most obvious ways to eat seaweed may be in sushi rolls or roasted seaweed snacks. But don’t stop there. “When I’ve used seaweed in dishes like oysters, guests are usually intrigued by the flavor and the visual appeal,” Packer says. “The Takaki Kaizo seaweed especially brings great texture and color, so it’s not just an accent but something that elevates the dish. Once people try it, they often comment on how refreshing it tastes.” You can typically find seaweed, especially dried varieties, in the international section of most major grocery stores. But for a wider selection, you’ll need to visit an Asian grocery store or shop online. 

Seaweed is mostly sold dried, and many recipes call for rehydrating it in water. To make seaweed salad, look for dried wakame and hijiki seaweed. Rehydrate the dried seaweed in a bowl of warm water until tender, which can take about 20 to 30 minutes. Then simply toss with a dressing made with miso, soy sauce, sesame oil and vinegar. Miyeok-guk, a Korean seaweed soup, is often made with rehydrated dried brown seaweed (called miyeok or wakame), garlic and sesame oil simmered in an aromatic broth. 

For an even easier way to add more seaweed to your diet, try sprinkling sliced toasted nori sheets over grain bowls, salads or crispy tofu. 

Our Expert Take

Seaweed farming may not be a silver bullet for climate change—but its environmental promise is real. From its role in carbon sequestration and methane reduction to its potential in sustainable packaging and farming, seaweed stands out as a rare win-win: nutritious, versatile and low-impact. And while the biggest benefits may come from how we use seaweed outside the kitchen, adding more to your plate is a healthy, sustainable step worth taking.