Seaweed Farming -- Climate Solution or Risky Profiteering Scam?

Holly Dressel
globe and seaweed

Oct 6 2022

In seaweed, climate capitalists see green

A boom in seaweed farming is being sold globally as a climate solution, but some Indigenous nations and local harvesters are sounding an alarm

In the inlets between Vancouver Island and the archipelago of the Georgia Strait, floats one of the largest seaweed farms in North America. 

Cascadia Seaweed’s floating grid of blue buoys plays host to seedlings of kelp and other species of seaweed growing on lines just below the water. After six months or so of growth, the plants are large enough to be harvested. A winch pulls the lines with dripping seaweed stalks attached aboard a steel-hulled boat en route to a processing facility. 

Founded in 2019 in Sidney, B.C., Cascadia’s operation has spanned as much as 44 hectares of coastal water, though it varies in size.

Their aim is to get a lot bigger, and quickly. 

Cascadia chairman and co-founder Bill Collins told local media in 2021 the plan by 2025 is to have 500 hectares under cultivation, with agreements on “at least 500 more.” 

The bulk of global seaweed farming to date—an estimated 97 per cent—has happened along Asian coastlines, with major producers like China, Indonesia and the Philippines providing for a rapidly-growing market. In recent years, Canada has also seen expanding activity and investment.

As the search for climate solutions grows ever more urgent, the global seaweed farming industry has attracted big investment capital, glowing press coverage—and the hopes of many environmental activists and groups. NPR, BBC, CBC and the Globe and Mail have all featured seaweed farming extensively, extolling its benefits for everything from climate change to warming and acidifying oceans.

This new vision for ocean coastlines has been greeted with enthusiasm by everyone from the B.C. Green Party to Lebron James and Bill Gates, who are among the high-profile investors in seaweed-based products. 

As more people become invested—financially and otherwise—in the seaweed rush, some scientists and critics are questioning the foundations of the big-time profits being promised.

Recent scientific research suggests that exponential expansion of the seaweed industry—particularly for the potentially massive market for carbon credits—could actually diminish resilience of oceans at a time when saltwater ecosystems are being hammered by acidification, rising temperatures and shifting ocean currents. 

While seaweed farming has been cautiously embraced by some coastal First Nations in B.C., further down the Pacific coast, a consortium of Indigenous Nations has rejected seaweed farming and is working to stop its expansion.

Differing views on seaweed can be traced to what happens to ecological systems and local livelihoods when the industry scales up by several orders of magnitude—and how much control and regulation will be possible once a global market for carbon credits gets momentum and an institutional foothold.

A seaweed farm in Fujian province, China. To date, the lion’s share of the rapidly-growing global seaweed cultivation industry has taken place in Asia.

Roots and stalks of an investment bonanza

Today, global seaweed farming harvests are largely used for food products (nori, salty kelp snacks, a thickening agent for ice cream), or for pharmaceuticals.

But what is fueling investor enthusiasm is the potential for some species of seaweed to be used for biofuel and carbon credits. 

First established in the 1990s, carbon credits monetize activities like tree planting, awarding one credit per tonne of carbon that is prevented from entering the atmosphere. Credits can then be bought by polluting businesses or individuals to cancel out the negative effects of their carbon emissions. 

At least, that’s the idea.

In practice, carbon credits have proven to be vulnerable to misinterpretation of data and lack of oversight. Some operations don’t capture as much carbon as they say they do. Some claim to capture CO2 when they actually don’t, and others actually stifle sustainable use of the land or displace communities from it—leading to increased carbon emissions and lost livelihoods for farmers and harvesters.

Emerging technology researcher Jim Thomas says that trying to isolate part of an ecosystem can lead to bad assumptions and lead proponents to downplay negative impacts.

He cites the example of “ocean fertilization,” a scheme intended to sequester carbon by dumping iron filings in the ocean. The filings stimulate the growth of phytoplankton, which would absorb carbon dioxide before sinking at the end of its life cycle, storing it safely on the sea floor—or so the theory went. 

The theory was too simple. Thomas, who is Director of Research at ETC Group, a “research and action” organization with offices in Quebec, Mexico and the Philippines, says that ocean fertilization on a scale that could put a dent in atmospheric CO2 levels could have deadly consequences.

“Artificial plankton blooms may be invasive, may use up oxygen needed by other species, and lead to dead zones in the ocean… they can produce lots of unwanted gases when the algae die off, like nitrous oxide, a greenhouse gas”.

In other words, it could make climate change worse.

For these reasons, ocean fertilization has been subject to a moratorium in international fora like the London Convention, the UN Convention on Biodiversity and the UN Convention on the Law of the Sea.

The burgeoning seaweed industry, Thomas explains, is based on a similar assumption: that growing vast amounts of seaweed can remove CO2 from the atmosphere.

Classified as agriculture, seaweed farming has been able to avoid bans while creating investor interest based on a belief it can generate carbon credits. 

Similar to plankton schemes, the idea is that when kelp and other seaweeds are not harvested, but die, they will sink to the ocean floor, taking the carbon they have absorbed with them. Farms growing ever larger amounts of seaweed, on this account, are potential carbon credit factories.


A kelp forest near La Jolla, California. Natural seaweed growth is on the decline due to human impacts and chemical effluents. Photo: Oliver Dodd

The murky science—and economics—of sinking seaweed

Science has very little understanding about what happens to dead seaweed once it’s on the sea floor. While carbon credit excitement is based on the idea that dead kelp will remain there and be covered by sediment, trapped for thousands or even millions of years.

But some researchers speculate that it may dissolve into the ocean, releasing its carbon and acidifying it further. It may be into ocean currents, ending up on land in a decomposed condition. 

And if dead seaweed keeps carbon out of the atmosphere under certain conditions, scientists say there’s no guarantee that it will do so if those conditions—temperature or currents, for example—vary. 

One study published this year suggests that increasing the amount of dead seaweed could even end up adding more carbon to the atmosphere than it absorbs—accelerating rather than preventing climate change. 

Worldwide, the number of places where plants can be used to sequester carbon are limited.

Planting trees and protecting forests and grasslands are popular ways to earn carbon credits, but the UN Intergovernmental Panel on Climate Change (IPCC) figures the maximum amount of carbon that can be stored is orders of magnitude below what’s needed. That’s what is driving so much attention to seaweed—it seems a new frontier to scale up carbon credits.

A big factor in the seaweed hype is the 2015 Paris COP decision to introduce the idea of “Net Zero”. Net Zero essentially means that through accounting—not by reducing emissions—companies can come to a technical version of zero emissions. Enbridge or Air Canada can continue to burn fossil fuels, but if they buy enough carbon credits, they can claim to produce “net zero emissions”.

“Because of Net Zero,” Thomas explains, “there’s this unprecedented pressure on financial markets to deliver carbon credits to every kind of polluting industry, so they can stay in operation.” The result is an urgent scramble to find techniques—mechanical or biological—to suck carbon dioxide out of the air, and to bury it underground or to sink it in the ocean.

To get around the problem of getting seaweed to stay under the ocean so it can get in on the carbon capture market, some farms, such as Running Tides in Maine, are aiming to physically sink the seaweed they grow, instead of harvesting it.

It’s also a question of scale. 

Even if the critical questions raised by some scientists turn out to be wrong and the seaweed sequestration industry is successful, estimates suggest a massive growing operation would only remove about 0.2% of annual global emissions. How massive? In that scenario, 63% of the global coastline would host a 100-metre-wide belt of kelp—covering a total surface area roughly the size of Panama. 

But while seaweed will only ever be a niche form of carbon capture in the global scheme of things, the potential for big profits under a Net Zero regime is nonetheless significant enough to drive a transformation of vast areas along the world’s coastlines.


Cascadia Seaweed installs new infrastructure near Cortez Island, B.C. in 2021. Photo: Cascadia Youtube

Last chance for ocean-based carbon capture?

Cascadia makes it clear that although their production is currently all used as human food, they see future potential for biomass for carbon credits, fertilizers and cattle feed. 

Market pressures and competition, however, could push the industry in directions that entrepreneurs may not have had in mind when they started out.

Because it’s limited to national territorial waters and classified as aquaculture, Thomas explains, seaweed farming is “the only large option not covered by the moratoria on algal schemes.” In other words, it’s the only game in town when it comes to harvesting carbon credits from the ocean.

“Even food-focused operations like Cascadia,” Thomas told The Breach, “can’t help but be influenced by this bigger, ravenous market for sequestration.”

Cascadia is currently enrolled in an ongoing study by Ostrom Climate Solutions on the feasibility of seaweed carbon sequestration and selling carbon credits. 

Production costs are currently too high for carbon credits to be viable, Cascadia’s Bill Collins said in a statement sent to The Breach.

“However, with increased scale of production, reducing sequestration costs, and innovation in biotech to improve yield, the future value proposition may exist,” added Collins, who is the company’s Chair.

Seeking to diversify the markets they sell to, seaweed farmers like Cascadia have also explored supplementing cattle feed with seaweed. There is some indication that seaweed can lower the methane production of cows, reducing a significant source of greenhouse gas.

Here again, science has introduced a wrinkle: a team at Wageningen University in the Netherlands recently confirmed that the same elements of seaweed that make cows belch less methane turn out to be two toxins—bromoform and chloroform—which can wind up in meat and milk. Indeed, seaweed tissues tend to concentrate toxic compounds, so large-scale use of seaweed feed could transmit the contents of polluted water to consumers of beef and milk.

A kelp forest near La Jolla, California. Photo: Oliver Dodd

Underwater alliances

“We are Indigenous people. We are here to conserve and protect the environment while we produce food and create opportunity for our people,”  Tsawout nation fisheries manager Chrissy Chen said of the nation’s partnership with Cascadia when it was first announced

“Cascadia Seaweed is supporting all of these objectives.”

Since it was founded three years ago, Cascadia has formed strategic alliances with organizations representing over a dozen B.C. First Nations. 

Coastal First Nations, an umbrella organization which represents nine B.C. First Nations, has been selling carbon credits since around 2012 based on sequestration in the Great Bear Rainforest, earning member bands around $4.5-million a year. They originally approached Vancouver’s Ostrom Climate Solutions to see if farming kelp could form the basis for carbon credits to bring in crucial revenues.

The CFN told The Breach it currently does not have a unified position on seaweed farming. A number of CFN’s members are working with Cascadia, but others are not. The Tsawout from East Saanich have a clear partnership, while others lease parts of their traditional coastlines to the company.  

It seems that many of these B.C. First Nations are doing their homework before forming partnerships.

Jay Ritchlin, who monitors the Great Bear Rainforest, salmon farming, and other coastal protection at the David Suzuki Foundation, says he is encouraged by the First Nations economic partnerships.

“I know at least one band doing serious primary science to see carrying capacity before they allow such industries,” Ritchlin told The Breach. Permission from First Nations to develop such industries, he notes, does not negate provincial laws applying to the same area. 

While he agrees that entry into the carbon credit industry could cause problems, Ritchlin sees the food and pharmaceutical branch of the seaweed industry as having a bright future—provided robust regulations are in place.

In northern California, some Indigenous nations are taking a markedly different approach.

The Sinkyone Council, which represents 10 coastal Nations in northern California, recently proposed at 10-year closure for commercial kelp harvesting, published a letter voicing their opposition to any equivalency between natural and wild seaweed systems and commercial ones, and tabled a proposal for much greater control over seaweed farming.  

The Sinkyone have made a long list of the “hazards and impacts” of seaweed farming in general, including: “entanglement, injury or death” of larger fauna in the platforms and ropes that support the farms; “severe changes to the planktonic communities” because of the shading created by the floating kelp rafts; “fossil fuel needs for harvesting and processing”. They point out that “surface drag” from the farms “dramatically changes nutrient absorption of naturally-occurring species”; along with “nitrogen effluent release and uptake, which quickly gets out of control, resulting in bacterial, viral and fungal overloads that may not be possible to remediate.”  

The growing seaweed industry, in the eyes of the Sinkyone member Nations, is something that is responsible for “compromising natural functioning of ecosystems” and therefore “endangers the interdependent cultural lifeways of Indigenous Peoples.”  

In many ways it is the opposite of the perspective taken by the most enthusiastic First Nations in B.C. 

A worker hand-harvesting seaweed near San Diego, California. Photo: Daybreak Seaweed

Defending the commons vs. expansion with best practices

The Seaweed Commons, an alliance of small producers and traditional gatherers of seaweed on both coasts of the U.S. and Canada, has expressed alarm at the rapid growth of seaweed production—between 2004 and 2015, the global harvest grew by 7.6 per cent each year. 

“In spite of the very fast growth of companies farming seaweed in B.C.,” reads a position paper published by the Commons, “there remain few regulations and very little oversight.” 

“There are no regulations around farm size, native seed collection and responsibility for farm-related marine debris.” 

By contrast, the rapidly-growing Cascadia is determined to position itself as a leader in best practices when it comes to Canadian seaweed production. Among other things, their team pays attention to how to avoid depriving other species of sunlight, and how kelp can help remediate areas of the ocean that suffer from nitrogen coming from land-based farms.

Cascadia imagines itself as part of a business model that operates “for the benefit of the planet, rather than at the expense of it,” Bill Collins said in a statement sent to The Breach.

“We strive to set a positive example with a business model that can be good for people and the planet.”

Unlike Northern California, which has seen giant kelp forests decimated by agricultural run-off, warming waters and disease, B.C. has the highest diversity of kelp species, with large, intact swaths of kelp forests providing habitat to five species of Pacific salmon and endangered killer whales. 

“Cascadia takes the position that seaweed cultivation is a net benefit to the coastal ocean environment,” a company spokesperson said. “It would be premature for us to take a position around regulation of the seaweed-based carbon market for the sole purpose of sinking it.”

Cascadia believes that farming can help bolster biodiversity and shore up the slow disappearance of wild kelp. “With declines in both salmon and kelp forests along BC’s coast, kelp farming has the potential to help regenerate both,” a statement on their website argues. The B.C. government has provided a grant for Cascadia and its First Nations partners to study the effects of 400 hectares of seaweed farms on juvenile salmon.

Meanwhile in California, the Sinkyone Council is fighting against similar initiatives.

“Kelp farming is a monoculture—the marine equivalent of terrestrial industrial tree plantations,” the Sinkyone letter states. “Monocultures differ from naturally functioning ecosystems in that they extirpate naturally occurring species and disrupt natural dynamics, lack biological diversity, act as foreign pathogen vectors, lack resilience to threats, and require cyclical harvesting.”

“There is a real risk,” the Sinkyone letter continues, that ”grant funding could be used by commercial kelp farmers to establish or expand kelp plantations under the guise of ‘conservation, restoration, or management of kelp forest ecosystems.’”


Protesters show their support for an occupation of a fish farm near Alert Bay in 2017. Some of the people who fought salmon farms for years are raising the alarm about a massive scaling up of seaweed cultivation. Photo: Rolf Hicker Photography via social media


The fallout from farming the sea

An industry in its early stages—working at a small scale, and led by idealistic entrepreneurs—often bears little resemblance to what it becomes when it scales up, and big investors get on board. 

Some who have battled salmon farming—another controversial aquaculture industry—are sharing warnings about seaweed.

Farming the sea through salmon and shrimp farms was initially greeted with the same kind of enthusiastic optimism that accompanies seaweed. Even when problems began to appear, the burgeoning industry waved them aside, either denying them or making tweaks in their methods. As it grew more entrenched economically, dealing with this industry—and its financial and political power—became extremely difficult.  

Today, however, B.C. salmon farms are slowly being closed down. The negative impacts on wild salmon—the infestations of sea lice and other diseases and problems—are now undeniable, even by supporters.  

Marine biologist Alexandra Morton is known for her devotion to the salmon populations of the B.C. coast. She isn’t totally opposed to seaweed farming. In fact, she’s an advisor to the Seaweed Commons and contributed to their position paper.

But Morton fears a repeat of a lesson only just learned.  

“The push for large kelp farms is a replay of the devastating mistakes committed during the onset of industrial salmon farming on the BC coast, causing incalculable damage to the wild salmon,” she told The Breach. Morton worries that kelp farming on an industrial scale could further impact life-sustaining marine ecosystems already damaged by salmon farms.

Oceans are suffering from high levels of human interference: unnatural warming, acidification, drag-trawling, agricultural run-off dead zones, massive overfishing, the destruction of food chain nurseries by shrimp farms, kelp decline and coral bleaching, not to mention the Pacific gyre of plastic waste.

Sea Shepherd founder Paul Watson helped Morton in her fight to prove that infestations harming wild salmon were coming from farms.  His comment about the rapid expansion of seaweed farms: “if we want to help the ocean heal, we have to leave it alone.”  

ETC Group’s Jim Thomas worries that despite the good intentions of some founders, investment-driven companies could pave the way for something decidedly un-ecological.

“Cascadia and companies like it may currently be small and claim to be focused on food,” Thomas told The Breach, “but they have used climate rhetoric, are exploring carbon credits, and are at the forefront of commercializing seaweed.” 

“Seaweed farms can be the wedge,” he fears, “leading to more efforts to interfere with ocean ecosystems, all in the name of climate remediation.”