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A commercial seaweed operation in Xiapu (China).Keren Su/China Span/Alamy
This story was first published by Hakai Magazine and is reproduced here as part of the Climate Desk collaboration.
Cornelia Rindt steadies herselfShe and her colleagues are in a rocking boat, while she and others lean over the side to grab a meter-long mud tube. It is her team’s first sample taken from the seafloor on British Columbia’s coastline. It will take over a week to collect six more samples.
“It’s as much of an art as it is a science,” says Rindt, a project developer for BC-based consultancy Ostrom Climate Solutions (formerly NatureBank). The coring device has to be lowered blindly through 100 meters of water—too deep for divers to navigate—and land vertically at the right speed, rather than bouncing off a rock or tipping over in the currents, in order to capture a good slice of the soft sediment below. The sample will then be sent to the lab to determine how many carbon is inside. It takes about five attempts to get a good specimen, she says. Sometimes they get nothing at all. Once, she remembers, the loose mud they pulled up flooded out of the tube before they could capture it: “That was 30 centimeters of sample that just went Whoosh. It was deep green and I could smell the carbon.”
The sampling is part of Ostrom Climate Solutions’s effort to help fill in the giant scientific blanks about kelp, the group of large brown algae that make up the oceanic “forests” of Canada’s west coast. The company is doing this at the request of Coastal First Nations (CFN), an alliance made up of nine First Nations from British Columbia. They are trying to find out how much kelp falls to the seafloor to be stored in sediment. Also, what is the effectiveness of kelp in locking up carbon and combating climate change?
That work is needed to back the global push to make the aquatic resource eligible for carbon credits—a sometimes-controversial scheme whereby people can earn credit for stopping carbon dioxide from reaching the atmosphere, and sell that credit on to companies aiming to counteract their own emissions. Some players believe seaweed, including kelps could join the carbon credit market as soon as this year.
CFN is excited about the idea. If seaweed qualifies to carbon credits, then CFN could earn hard cash for restoring kelp or farming it. Their communities “are very excited, because it’s a sustainable way of generating some income and giving back [to the ocean],” says Christine Smith-Martin, executive director of CFN who is from the Haida and Tsimshian First Nations.
Ostrom Climate Solutions isn’t alone in doing the science to back that idea. Global efforts to understand the carbon potential for seaweed have also been spearheaded by Oceans 2050—an initiative cofounded in 2020 by Alexandra Cousteau (granddaughter of Jacques-Yves Cousteau and a well-regarded environmental activist in her own right) aiming to Restore global ocean abundance. Like Ostrom Climate Solutions, they too are in the midst of their initial research into just how much carbon is stored under seaweed—and how much credit someone would deserve for helping seaweed to do that job.
Launched in October 2020, Oceans 2050’s 15-month seaweed research project has cored the seafloor under 21 seaweed farms in 13 countries on five continents. While most of these are located in Asia, one is very close where the Coastal First Nations live. Cascadia Seaweed, a three-year-old endeavor that has kelp farms in Barkley Sound, on the west coast of Vancouver Island, is Oceans 2050’s sole representative on the west coast of North America.
According to Carlos Duarte (chief science advisor behind Oceans 2050), seaweed farming is an important contribution to restoring ocean life and reducing climate change. Duarte envisions a world where there are four million square kilometres of seaweed farms around the globe (2,000 times the area of the current 2,000). This would create a thriving ecosystem of fish and generate billions of dollars annually for farmers. That’s a multibillion-dollar industry that hasn’t yet gotten started—but which could transform the oceans and a small slice of the carbon economy over the coming decades. Duarte calls it the “seaweed aquaculture imperative.”
Matemwe, Tanzania – Workers tend to seaweed I
mage Professionals GmbH/Alamy
Carbon creditsSince the 1990s, they have been around. Projects that sequester carbon—like tree planting—can earn one sellable credit for every tonne of CO2 equivalent that is prevented from entering the atmosphere. The market is a simple concept with a complicated history. Credits have, for instance, perversely incentivized businesses to raze one tree in order to plant another or to avoid decarbonizing themselves.
Numerous non-profit organizations monitor the voluntary market to verify carbon credits and police them. The most widely used of these registry services is Washington, DC–based Verra, which runs the Verified Carbon Standard offset program. The United Nations climate conference in Glasgow, Scotland, COP26, which took place this November, gave a major boost to the voluntary carbon credit market by adopting new rules that allow countries to partially meet their emission targets by purchasing offsets. It’s a change that has helped to legitimize the market.
So far, Verra has certified more than 855 million carbon credits, almost entirely for land-based projects including avoided deforestation and reduced emissions from manufacturing—sectors that were better understood scientifically and had larger-scale projects already underway in the market’s early days. Verra only recently added marine-based or so called “green” carbon credits. blue carbon to their registry, from projects that conserve, restore, or expand mangroves, salt marshes, and seagrasses. Observers believe that seaweed farming is next in line. Verra launched the first ever seaweed farm in August 2021. Seascape Carbon Initiative to help advance the blue-carbon market. “Seaweed farming has a lot of potential,” says Anne Thiel, communications manager for Verra.
The blue-carbon market has a smaller scope than its land-based counterpart but the price tag is often higher. That’s because companies are willing to pay more for carbon credits that have side benefits for local populations and ecosystems, and that come with publicity-friendly stories and photos that buyers can paste into their advertisements and annual reports. Blue-carbon credits are more expensive than land-based-forestry carbon credit. However, they can be sold for as little as US $1 per credit.
Advocates say seaweed is a good candidate to receive these blue credits. Seaweed grows quickly and can absorb 20 times more carbon than terrestrial plants of the same size. Admittedly, quite a lot of the uptake is only temporary: seaweeds don’t have roots to channel carbon underground; they often bloom and decline seasonally and can be wiped out by occasional storms or surges of predators like sea urchins; algae that are eaten by fish or decay release carbon back into the atmosphere; and bits that fall to the seafloor can be kicked up again by trawling. However, some seaweed carbon remains in the seafloor for the long term: oil deposits that have been found to be made from degraded macroalgae have been confirmed. This carbon is what makes seaweed so exciting as a climate change mitigation tool.
Duarte and Dorte Kruuse-Jensen gathered the evidence in 2016 and Estimate that seaweeds worldwide sequester a nontrivial amount of carbon. According to a Report from the High Level Panel for a Sustainable Ocean Economy (Ocean Panel), it’s about 640 million metric tons of CO2 equivalents annually. The margin of error is large: it could be a third or half of that again. The land-based forests, however, dwarf the total. They absorb up to 80% of the total. More than 10x more than macroalgae (even when accounting for deforestation); but seaweed is still a significant carbon sink.
The Ocean Panel report also states that seaweed covers a relatively small area of the world’s coast, which is more than India. Some spots may not be accessible. Climate change has ravaged the environment.The total area covered has decreased by less than one percent over the last 50 years due to pollution or other factors. This means that the biggest potential for boosting seaweed’s total carbon storage lies not in restoration projects (as is often done with mangroves, for example) but instead with farming. The Ocean Panel estimates that seaweed agriculture could absorb between 50 and 290 million metric tonnes of CO2 equivalents each year. Duarte’s published estimate is 239 million metric tons by 2050, equivalent to the annual emissions from about 52 million cars.
That’s still just a tiny sliver of less than one percent of global emissions, which are on the order of 50 Billions An average of 5.5 tonnes of CO2 equivalents per year. Global warming advocates say that every bit helps. “Many people argue that if the number is not in the billion [metric ton] scale then don’t bother,” says Duarte, “but I tell them there are no low-hanging [billions].” We need to start with the millions, he says, and then ramp up to the billions.
Duarte and others point out that seaweed has many side benefits. It can improve water clarity and biodiversity. Reduce ocean acidityFor shellfish farms, they absorb CO2. Seaweed farming is a low-cost, sustainable way to grow seaweed. It also absorbs CO2 and provides employment opportunities for women working in developing countries. Duarte claims that seaweed farming can be sustained and without major impacts, despite critics’ concerns about the industry’s rapid expansion. “Seaweed farming is actually a good thing to do, within some bounds,” says Duarte. “The scope for growth is about 2,000-fold.”
However, the profit margins from selling seaweed for sushi, seaweed snacks and other products is too small to support the need to save the planet. To Duarte’s eye, adding carbon credits to the mix could make it a far more appealing enterprise for farmers.
It’s this winning combination of finance plus environmental protection that made the whole idea of carbon credits catch the attention of CFN in the first place. CFN was the first to start selling carbon credits earned from avoiding deforestation. Great Bear Rainforest in their territory on the northern BC coast. They are able to sell half of their credits and earn over a million credits annually. They currently make $4.5-million a years, and that’s with room for growth. Each credit costs more than CAN $10. CFN asked Ostrom Climate Solutions (then NatureBank), if they could do something similar at sea. Could they get cash credit to grow kelp?
No one knows what the science base and data are, as they are very limited. Rindt was on the water in summer 2021 to collect samples from below natural kelp areas. “We’re kind of at this early stage of understanding,” says Rindt. Despite the challenges of core the seafloor at 100m depth in sometimes-difficult weather and a pandemic, the team was able to collect seven good samples at five sites on Vancouver Island’s northern tip and the mainland coast further north. These samples were sent to the lab to be analysed for carbon and kelp content. They are awaiting their results and plan to sample more spots along BC’s coast.
For the Oceans 2050 project, seaweed biologist Jennifer Clark helped to collect a few samples from under Cascadia Seaweed’s farms in 2021. Divers could also do the job, as they are more shallow. Meanwhile, other farms around the globe were doing the same and sending all their samples for analysis to a lab located in Monaco. Oceans 2050 had complete data for five farms at the end of 2021. Duarte states that the results roughly match his. calculated estimate of three metric tons of CO2 being stored in sediments per hectare—but with a huge range, depending on everything from the type of seaweed to the local ocean currents and whether the seafloor is rocky or not.
Duarte says that the initial results are encouraging, especially in tropical regions. They expect that their full results will be presented by March 2022.
When all the data is in, it needs to be converted into a solid methodology for carbon credits—a rule book determining how many credits someone can earn, and the steps they’ll need to take to prove it. Individual farmers could use default carbon credits values that are based on data such as seaweed type or water depth. Or, they could do their own coring to demonstrate their unique potential for carbon storage. Duarte estimates that a seaweed farmer could earn tens of thousands of carbon credits per hectare per year. “All we have now is hand-waving,” he says. Verra confirms that Oceans 2050 has submitted a “concept note” for a new methodology for seaweed farming, the first formal step in the carbon-credit approval process. CFN and Ostrom Climate Solutions haven’t yet chosen the verification scheme they’ll go with.
Until approved, kelp carbon credits aren’t a reliable cash cow. “In my view, it’s too early for seaweed harvesters to be trying to jump on the carbon bandwagon,” says Bill Collins, marine geologist and founding partner of Cascadia Seaweed. “It needs to be led by science.” For now, Cascadia has 20 hectares of farm, with plans to ramp up to perhaps 1,000 hectares in the future. Extrapolating from Duarte’s rough figures, that means they could eventually earn on the order of 10,000 credits a year, with a value of about $100,000 at prices around $10 per credit. Overall, Collins suspects there’s more profit to be made in kelp products than in carbon credits. But if kelp gets formally recognized—by being added to Verra’s books, for example—“we may get more excited,” he says.
Collins suggests that there might be more environmental ways to look at seaweed than focusing solely on carbon storage in sediment. “My instinct is that there will be better support for the planet by growing it and feeding it to cows,” he says. The largest share of greenhouse gas emissions from livestock is surprisingly large (14.5 percent of global totalThis is largely due to methane gas burps from ruminants. Previous research has shown that red seaweed can be added to feed. These emissions can be reduced by as much as 82 percent. That’s a whole other way that seaweeds might qualify for carbon credits—but, in this case, it would be the cattle farmers, not the seaweed producers, claiming those credits and getting that cash. Similarly, kelp can be turned into all manner of products—Textiles, concrete, and more—that would store the carbon away for the long term.
“It’s pretty exciting,” says Smith-Martin about the possibilities of incorporating carbon credits into the CFN’s efforts to holistically protect the land and sea. “I’m pretty sure our ancestors would have seen the value.” Each First Nation in their alliance, she notes, has their own plans for how they might incorporate kelp carbon credits into their coastal management, but all are excited about the opportunities for jobs, for expanding productive coastal ecosystems, and for a possible novel cash stream. “You don’t get very many opportunities to build on the abundance that we do have, or we did have at one time in our oceans,” she says. “It’s an exciting time.”
However, for now, the real excitement is taking place in the labs. Rindt and Duarte are scouring the data to introduce seaweed into carbon-credit markets. They first have to sort through some mud tubes to get to the future of profitable, lucrative kelp farming.
