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Europe considers large-scale seaweed farming; environmental effects unknown

Sea spaghetti in a kelp forest.

Sea spaghetti in the kelp forest off Bantry Bay, Ireland. Like rainforests, seaweed forests are among the most productive and species-rich ecosystems on earth. Image by Ingrid Gercama for Mongabay.

  • The European Commission is planning large-scale industrial farming of seaweed across the continent’s shores.
  • The goal is to farm 8 million metric tons of seaweed annually by 2030, up from the current annual farmed production of about 3,000 metric tons.
  • Proponents tout a sustainable form of farming that can produce food, chemicals, pharmaceuticals and biofuels, and sequester carbon.
  • However, the potential ecological impacts have yet to be fully assessed.

BANTRY BAY, Ireland – Claire O’Sullivan runs her small family firm, Wild Atlantic Seaweed Ireland, out of her house a short walk from Bantry Bay on the country’s southwestern coast. Her wild kelp is hand-harvested, a sustainable and traditional method of collecting seaweed. The company focuses on niche high-end products: Seaweed Infused Beard Oil, €15.00 for 50 milliliters ($14.66 for 1.7 fluid ounces), and Chilli and Lemongrass Seaweed Pesto, €5.60 for 100 grams ($5.43 for 3.5 ounces).

Since seaweed is packed with vitamins, fiber, protein and antioxidants, it has joined kale and quinoa to become a superfood. “My grandmother swore by carrageen moss,” O’Sullivan says. “She had everyone eating seaweed and she lived to be 103 years old. And my nanny was the same and she reached 100.”

But O’Sullivan’s company is only a tiny part of the massive global seaweed industry, currently worth an estimated €40 billion ($39.2 billion). According to the U.N.’s Food and Agriculture Organization (FAO), the world harvested 35.8 million metric tons in 2019. Asia accounted for 97% of total production, of which China produced 57%.

Claire O'Sullivan hand-harvesting wild seaweed.
Claire O’Sullivan hand-harvesting wild seaweed for her company, Wild Atlantic Seaweed Ireland, which makes pesto, soap and chocolate in Bantry Bay, Ireland. Image by Nathalie Bertrams.

Now Europe wants in. Along with Ireland and other member states, the European Commission is planning large-scale industrial farming of seaweed across the continent’s shores. The goal is to farm 8 million metric tons of seaweed annually by 2030, according to a statement the commission provided to Mongabay, up from Europe’s current annual production of farmed seaweed of about 3,000 metric tons.

Seaweed for Europe, an industry lobby group based in Brussels, worked with the European Commission to develop this goal. Kelp cultivation “provides essential food and habitat to the ocean ecosystem, and it’s a form of farming that needs no fresh water, fertiliser or cleared land,” Adrien Vincent, an associate at the lobby group, wrote in an email. “It can be a really important part of a sustainable and healthy ocean economy.”

If the goal of 8 million metric tons per annum is achieved, Vincent estimates that the European seaweed industry’s market value in 2030 would be €9.3 billion ($9.1 billion).

The commission and the European Investment Fund are providing €1.5 billion ($1.47 billion) of financing for the blue economy, and the industry is moving ahead. However, the science hasn’t caught up. The potential ecological impacts of nutrient depletion, genetic pollution and disease have all yet to be assessed completely.

“As the global seaweed aquaculture industry grows and diversifies, the risk of introducing known and emerging pests and diseases to the new regions will escalate,” Elizabeth Cottier-Cook, a marine biologist with the Scottish Association for Marine Science, points out in a 2021 policy paper. “However, there is no co-ordinated global effort to support seaweed research, to build and to transfer technical capacities and to protect wild seaweed populations.”

Seas At Risk is a coalition of 30 organizations working to protect Europe’s marine environment headquartered in Brussels. The organization’s marine policy officer, Marc-Philip Buckhout, has a more cautious view of large-scale seaweed production than lobby groups like Seaweed for Europe. “I have a worry that it is the next green thing,” he says. “And that in a few years from now, when we are more aware of the negative implications, the hype is going to be met with a bit of a reality check.”

A sea urchin.
Kelp forests serve as nurseries and habitats for many fish, crabs, worms and invertebrates such as sea urchins, and provide food and perfect shelter for seals and other mammals. Image by Nathalie Bertrams for Mongabay.

Growing between wind farms

One of the critical requirements for the kelp industry’s growth is “automation/industrialisation to allow for scaled production,” Lisa Evers, a press officer with Ireland’s Department of Agriculture, Food and the Marine wrote in a statement. That is precisely what is being developed in the Netherlands.

The Netherlands initially considered allocating 14,000 square kilometers (5,405 square miles) out of its 57,000-km² (22,000-mi2) North Sea exclusive economic zone for seaweed cultivation, but is now planning for a total of 400 km² (154 mi2).

Seaweed would first be cultivated in nearshore hatcheries until the plants are robust enough to be hung out in the farms. These would be in existing and planned offshore wind parks. The seaweed would then grow in the open ocean on nets, which would be attached to long floating tubes that in turn would be anchored with concrete blocks on the seafloor.

Since the waters between the wind turbines are restricted, seaweed farming is one of the few activities that could make use of the space.

The basic concept is to develop “a sustainable resource for the European markets. So that we may have a more circular way of living in the future,” Eef Brouwers, the manager for farming and technology at the Hague-based lobby group North Sea Farmers, says. “That’s a great dream. But then you have to try to realize it in practice.”

The Seaweed Company’s hatchery.
The Seaweed Company’s hatchery in the Oosterschelde, Netherlands. The mother plants come from the wild and are propagated in the hatchery and grown into a gametophyte culture. After fertilization, the sporophytes are sprayed on seed lines and grown in the hatchery until the young plants are robust enough to be hung out in the farms. Image by Tristen Taylor for Mongabay.
The coast near Bantry Bay.
The coast near Bantry Bay, Ireland. The Irish government seeks to develop large-scale industrial seaweed farming off the Atlantic coastline. Image by Tristen Taylor for Mongabay.

In June 2022, North Sea Farmers successfully tested a mechanical harvester at its offshore test site, 12 km (7.5 miles) from the Dutch port of Scheveningen — so far the only existing offshore farm in the Netherlands. The harvester cuts seaweed off nets attached to 50-meter- (164-foot-) long tubes and brings it aboard a ship. Without this kind of technology, farming at an industrial scale is simply not possible.

With the technology advancing rapidly, policy and regulatory support from national governments and funding from the EU, the vision for large-scale seaweed farming is increasingly likely to become a reality for industry players like North Sea Farmers’ 100 members. The food giant Cargill helped to set up the lobby group, whose current members include Unilever, Shell and the Swedish energy company Vattenfall.

Brouwers says he thinks it is too early to talk about the ecological impact of large-scale seaweed cultivation. “We need to reach a certain scale first to find out what will happen. Of course there is data on seaweed cultivation, but not in an offshore situation. The dynamics here are completely different. We don’t yet know what the environmental impact will be,” Brouwers says.

A mechanical arm on the Janne Yerseke cuts seaweed off a rope.
A mechanical arm on the Janne Yerseke cuts seaweed off a rope at the North Sea Farmers’ test site 12 km off the Dutch coast. The test is a technological milestone for commercializing large-scale seaweed farming in the North Sea. Image by Nathalie Bertrams for Mongabay.

Uncertain environmental consequences

Reinier Nauta is a seaweed researcher at Wageningen University in the Netherlands and one of the few scientists trying to figure out what the impacts of large-scale seaweed farming in the North Sea would be.

“To place 14,000 km² of seaweed cultivation in the North Sea you would drain it completely from all the nutrients that are there,” Nauta says. “With that you drain [the nutrients] from all the fish and everything else in the higher trophic levels. So you’ll end up with a barren area with no life in it.”

On the other end of the spectrum, he says a couple of square kilometers would certainly be safe. Beyond that, he says he simply doesn’t know if it will be safe to go ahead with the planned 400 km².

Nauta’s current research looks at the danger genetic pollution may pose to the natural diversity of wild kelp. As seaweed becomes domesticated for farming, it becomes increasingly ennobled. “You might end up with a stronger individual, or a stronger genetic strain than wild types might be. And you want to avoid mixing those things,” Nauta says.

Seaweed travels far and wide, and the potential for cultivated strains and diseases alike to spread is significant. There’s a high likelihood that storms, waves and even the harvest process would detach seaweed from their lines. According to Nauta, seaweed from Dutch farms can end up in Danish waters within a week.

As for how long it will take to assess the potential environmental consequences properly, Nauta’s answer is direct: “10 to 15 years.”

A kelp forest.
The kelp forest off Bantry Bay, Ireland. Like rainforests, kelp forests are among the most productive and biodiverse ecosystems on earth. Image by Ingrid Gercama for Mongabay.

A superfood with industrial properties

The Bantry Marine Research Station is almost at the mouth of the bay. With EU funding, the outfit has assisted the Irish government in developing plans to increase the Irish seaweed industry vastly through industrial farming and produce 10,000 metric tons annually within the next five to 10 years, aiming the crop at the food, cosmetics and pharmaceutical sectors.

Julie Maguire, the station’s director, says she is also excited about using seaweed’s tough but stretchable sugars to make edible food packaging.

In terms of large-scale seaweed farming in Europe, she says, “I think it’d be great. I’d love to see it, like, I really would.”

Extracts from seaweed such as carrageen, also known as E407, are vital for the industrial production of food and other products. Seaweed extracts are used as binding, gelling and stabilizing agents in a wide range of goods: everything from ice cream to salad dressings, shoe polish and soy milk.

Put another way, the kelp industry isn’t primarily about organic face creams and vegan sausages, it is about chemicals and processed food. Multinational corporations such as Cargill, Unilever and Nestlé require E407 and other extracts to make their products, and a lot of it.

“Seaweed is sought after by quite a lot of chemical companies that like to source not from microfarms but large-scale farms,” Buckhout from Seas At Risk says.

Giant wild kelp under water.
Giant wild kelp in Bantry Bay, Ireland. Image by Ingrid Gercama for Mongabay.

Biofuels and subsidies

“Algae are the ‘ocean gold,’” Virginijus Sinkevičius, Europe’s present commissioner for environment, oceans and fisheries, said in a 2019 speech. “Processed as biofuels or bioplastics, they turn their petrochemical alternatives obsolete. Using just 10% of the unused space in North Sea wind farms for algae production would absorb yearly emissions of all cars in Europe.”

Given Russia’s invasion of Ukraine and Europe’s urgent need for new energy supplies,  biofuels from energy-dense seaweed like sugar kelp (Laminaria saccharina) are receiving renewed attention.

Jaap van Hal is a biofuels expert at the Dutch research organization TNO and helped to develop the country’s policy of allocating 400 km² of the North Sea for seaweed cultivation. “A world scale bio ethanol plant processes 1.2 million [metric] tons of grains dry matter basis,” he says.

A plant processing seaweed would require a similar amount. “That is several orders of magnitude, meaning thousands of times bigger than the current fields of several hectares,” van Hal says. “They need to go to hundreds and hundreds of square kilometers.”

Drone image of snorkelers at the edge of a kelp forest.
Snorkelers at the edge of a kelp forest in Bantry Bay, Ireland. Image by Tristen Taylor for Mongabay.

Given the substantial biomass required, one idea scientists with the EU’s Horizon 2020 research program are looking into is that seaweed washed up on beaches could complement the feedstock from cultivation.

Brouwers of the lobby group North Sea Farmers points out that the industry is not yet financially viable: wild harvesting still accounts for about 99% of Europe’s annual seaweed production and thus determines the per kilogram price. Wild kelp is a free resource unlike cultivated seaweed. His solution is to “introduce a subsidy scheme or cost price compensation scheme, similar as you see in agriculture in Europe, then [seaweed farming] could become profitable.”

Carbon not sunk at sea

The idea behind using kelp to sequester carbon is straightforward. Given that seaweed absorbs carbon dioxide quicker than terrestrial plants of the same volume, carbon could be sequestered by sinking fully grown seaweed to the bottom of the ocean where the carbon would be locked away.

European farmers could cultivate kelp specifically to sequester it, so-called “blue carbon farming.” They could then sell carbon credits, in the same manner that tree planting can generate carbon credits, and this could be a vital revenue stream for the industry. The European Commission is currently exploring blue carbon farming of seaweed as part of the EU’s strategy to become climate neutral by 2050.

Researchers at the Institute for Marine and Antarctic Studies at the University of Tasmania aren’t convinced about seaweed farming’s climate mitigation potential. In a 2022 study, they found that the eating and breathing of organisms living among seaweed makes seaweed ecosystems natural carbon sources, not sinks. And they point out that many broken-off fronds decompose or get eaten before they ever reach the seafloor, emitting even more carbon dioxide.

Seaweed on the coast.
Seaweed along the coast of Bantry Bay, Ireland. Image by Tristen Taylor for Mongabay.

“Any efforts to quantify seaweed carbon storage and mitigation for the protection, restoration or farming of seaweed must make a full accounting of carbon inputs and output to ensure we are not unwittingly making the problem worse rather than better,” the paper’s lead author, John Barry Gallagher, wrote in a synopsis.

To sequester carbon effectively, seaweed must be sunk at least 3,000 meters (9,843 feet) below the surface. The maximum depth of the North Sea is 700 meters (2,296 feet) and the average is 90 meters (295 feet). A deep-sea canyon 3,000 meters deep exists off Ireland’s Atlantic coast, but it is 320 kilometres (199 miles) from shore.

According to the FAO, the ecological impacts of large amounts of seaweed covering the seabed remain unknown.

Back in Bantry Bay, Claire O’Sullivan says she’s unconvinced industrial seaweed cultivation in the Atlantic will pay off. “That would concern me massively; I imagine like most large-scale farming, it will be detrimental to the environment,” she says. “Projects like that I feel are short-sighted and they’re all about the fast buck.”

Banner image: Sea spaghetti in the kelp forest off Bantry Bay, Ireland. Like rainforests, seaweed forests are among the most productive and species-rich ecosystems on Earth. Image by Ingrid Gercama for Mongabay.

This reporting was supported by the International Women’s Media Foundation’s Howard G. Buffett Fund for Women Journalists and the Postcode Lottery Fund of Free Press Unlimited.

Correction 10/29/22: This article originally misattributed statements about the quantity of seaweed needed to support energy production to Sander van den Burg, a biofuels expert at Wageningen Economic Research of Wageningen University. In fact it was Jaap van Hal who made the statements. It also misstated the amount of material a bio ethanol plant can process: it is 1.2 million metric tons of grain, not 1.2 billion metric tons. We have updated the story to reflect these facts. We regret the errors.


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