For centuries, it’s been treasured in kitchens in Asia and neglected almost everywhere else: those glistening ribbons of seaweed that bend and bloom in cold ocean waves.
Today, seaweed is suddenly a hot global commodity. It’s attracting new money and new purpose in all kinds of new places because of its potential to help tame some of the hazards of the modern age, not least climate change.
In London, a startup is making a plastic substitute out of seaweed. In Australia and Hawaii, others are racing to grow seaweed that, when fed to livestock, can cut methane from cow burps. Researchers are studying just how much carbon dioxide can be sequestered by seaweed farms as investors eye them as a new source of carbon credits for polluters to offset their greenhouse gas emissions.
And in South Korea, one of the most established seaweed-growing countries in the world, farmers are struggling to keep up with growing export demand.
What was mainly a relatively small Asian industry is now coveted by the West. Far beyond South Korea, new farms have cropped up in Maine, the Faeroe Islands, Australia, even the North Sea. Globally, seaweed production has grown by nearly 75% in the past decade. The focus is moving far beyond its traditional use in cuisine.
But even as its champions see it as a miracle crop for a hotter planet, others worry that the zeal to farm the ocean could replicate some of the same damages of farming on land. Much is unknown about how seaweed farms, particularly those far offshore, can affect marine ecosystems.
“Seaweed protagonists believe seaweed is a cure to everything, that seaweed is a magical panacea for climate problems,” said David Koweek, chief scientist for Ocean Visions, a consortium of research organizations studying ocean-based interventions for the climate crisis. “Seaweed antagonists think seaweed is completely overhyped.”
There’s another problem. Seaweed is itself feeling the impact of climate change, particularly in Asia.
“The water is way too hot,” said Sung-kil Shin, a third-generation seaweed farmer, as he pulled his boat into harbor one morning on Soando Island, just south of the South Korean mainland, where seaweed has long been foraged and farmed.
‘Plastic’ from seaweed
Pierre Paslier once made a living by designing plastic packages for cosmetics. It felt to him like “leasing out my brain to a big plastic polluter.”
He wanted out. He wanted to create packaging that would come from nature and disappear into nature, quickly. With a friend from graduate school, Rodrigo García González, he created a company called NotPla, short for “not plastic.”
From an East London warehouse, they designed an edible sachet of water, made of seaweed and other plant extracts: To drink the water, you simply pop the sachet in your mouth. They designed another one that can hold ketchup and a third for cosmetics.
They also began making a seaweed-based coating for takeout cardboard boxes. Just Eat, a food delivery app in Britain, began using it for some of its orders, including at the European women’s soccer finals in July at Wembley Stadium.
It’s still niche. The seaweed coating, designed for home composting bins, is considerably more expensive than the plastic coating now used on most takeout boxes made of paper.
But Paslier is looking to the future. The European Union has a new law restricting single-use plastic. A global plastics treaty is under negotiation.
Foragers from the past
In the gray light of dawn, Soon-ok Goh, a slight 71-year-old, swam soundlessly in the shallow waters of Gijang, on the southern coast of South Korea. Her feet were sheathed in yellow flippers, her thin, small frame in a wet suit. She surfaced above water for a few seconds, took a long breath that sounded almost like a whistle in the quiet of the morning, then dived down again, yellow flippers upturned.
Goh is among the last practitioners of a vanishing trade. Since the end of the seventh century, women like her have foraged for wild seaweed, along with other seafood, in the chilly waters around the Korean Peninsula.
This morning, a tiny pink-handled knife in hand, she snipped shiny green-brown ribbons of kelp called miyeok. She plucked sea snails clinging to rocks, two kinds of sea cucumbers, a handful of kelp-devouring sea urchins.
All went into her sack.
In decades past, when there was no money to buy rice, you could go to the sea and find seaweed, said Hye Kyung Jeong, a food historian at Hoseo University in Seoul, South Korea. “Seaweed helped people survive during famines,” she said.
This is not the first time seaweed has helped avert a crisis.
Slimy arms race
The new frontier for seaweed production lies beyond Asia.
Steve Meller, an American businessperson in Australia, grows seaweed in giant glass tanks on land — specifically, a red seaweed native to the waters around Australia called asparagopsis, which beef and dairy companies are eyeing as a way to meet their climate goals.
A sprinkle of asparagopsis in cattle feed can cut methane from their burps by between 82% and 98%, according to several independent studies. Cattle burps are a major source of methane, a potent greenhouse gas.
“The race is on, I suppose, to get the world’s first commercial supply,” Meller said. “The demand is off-the-roof scale.”
His company, named CH4, after methane’s chemical formula, is competing to bring asparagopsis to the mouths of cows. At least two other Australian startups, Sea Forest and Rumin8, are in the seaweed-for-cattle race. So are Symbrosia and Blue Ocean Barns, both in Hawaii.
Fonterra, a New Zealand dairy producer, has begun commercial trials of the seaweed supplement, and Ben & Jerry’s is planning its own trials soon. The global dairy giant Danone has invested in an asparagopsis startup.
Whether seaweed can make a dent in cattle methane remains unclear. In the United States, there’s another hurdle to overcome: regulatory approval.
Nevertheless, it could be key to the beef and dairy industry’s ability to meet climate goals. Emissions from food systems alone, mainly meat and dairy, could raise the global average temperature by 1 degree Celsius by the end of the century, blowing past the threshold of relatively safe global warming, researchers have said.
Seabirds dive and squawk around the fishing port in Soando, an island off the southern tip of South Korea, as Shin’s boat pulls in with the morning’s harvest.
Shin, 44, has plied these waters for 20 years and has seen climate change upend his trade. He grows a red kelp species called pyropia, which favors cold water during its growing season. So he has been going further and further from shore in search of chilly waves.
By mid-April, Shin said, the water isn’t as cold as pyropia likes. His yield has suffered. “People want more seaweed these days,” he said. “But there’s no more seaweed.”
Since 1968, the waters where Shin farms have warmed by 1.4 degrees Celsius, slightly higher than the global average. That’s why South Korean scientists are racing to breed strains that can thrive in warmer waters.
Seaweed farms are a far cry from the rows of corn and wheat that make up monoculture farming on land. But even as they signify new opportunities, they present ecological risks, many of them unknown.
They could block sunlight to creatures who need it below. They could scatter plastic buoys in the sea, which already suffers from too much plastic. They could leave their plant detritus on the seafloor, altering the marine ecosystem.
“It needs to be carried out with a great deal of care,” said Scott Pillias, a doctoral student in economics who studies marine systems at the University of Queensland. “We shouldn’t expect seaweed to save us.”