Could seaweed be the "fastest and cheapest" tool to combat climate change?

A wave of startups say seaweed is a multi-pronged solution to climate change: It can absorb carbon, curb the effects of methane hiccups in cattle, and provide biofuels — not to mention the world.

A wide variety of Gulf of Maine seaweed in purple, gold, and green sparkle in the lights, including sugar kelp, sea lettuce, dulse, bladderwrack and Irish moss. Seaweed is considered a multifaceted solution to climate change, locking in carbon dioxide... Show more

Pass by Bridget Huber photos

Written by Lauren Owens Lambert Posted on June 2, 2023 • 11 min read

The story is in partnership with the Food & Environment Reporting Network, a nonprofit investigative journalism organization.

Iceland is conducting a bold experiment to use seaweed as part of a solution to climate change, where millions of small buoys made of wood and limestone, some seaweed, will be released into the ocean in the coming months.

Running Tide, the Maine company behind the project, is developing a system that will eventually sink buoys decorated with long bundles of seaweed to the deep ocean floor, and the carbon contained in the buoys will be sequestered for 800 years or more. It's hard to set a timeline: nothing like this has ever been done before.

The company is part of a new batch of startups that are positioning seaweed as a multi-pronged solution to combat climate change — capable of absorbing atmospheric carbon, reducing methane emissions from cattle, providing feedstock for biofuels, and feeding the world — without the need for fertilizer, fresh water or even land. Some of these businesses, such as Running Tide, want to sink seaweed into water to remove carbon from the atmosphere. Others hope to replace carbon-intensive materials such as soybeans, fertilizers, plastics and oil with seaweed-derived products.

Natalie Colao, a technician at the Running Tide macro seaweed hatchery in Brunswick, Maine, weighs and photographs individual seaweed every week.

However, if seaweed proves to be an effective tool for stabilizing the climate, the industry will need to expand substantially. Some scientists, small harvesters and environmental groups warn against rushing until basic scientific, environmental, regulatory and ethical issues are resolved.

Kristen Davis, a professor of civil and environmental engineering and earth system science at the University of California, Irvine, said climate change is intensifying and people are "panicking." But, she said, seizing on seaweed-based carbon removal as a solution until the science is determined could cause environmental damage or distract attention from more credible strategies, such as rapid emissions reductions.

"Science hasn't confirmed that this is a good idea," Davis said.

A potentially perfect solution

Running Tide, which operates at Portland's Fish Terminal, was founded by Marty Odlin, an engineer and fourth-generation commercial fisherman. The Gulf of Maine is warming faster than almost any other ocean area, and Odrin has seen the changes firsthand: fish migrating north to colder oceans, clam shells dissolving in acidified water.

Team members of the Run Tidal team search and collect seaweed tissue and various algae samples at Jewell Island in Casco Bay, Maine. Souri is the reproductive tissue on kelp leaves that is used to breed kelp in hatcheries.

About 15 years ago, Odrin listened to a lecture by Klaus Lackner, a physicist who popularized the idea of removing carbon from the atmosphere. Hit it off. "It's like, oh, that's right, because we can't get rid of fossil fuels in the next 50 years," he recalled. "We're going to have to tear it down."

A recent assessment by the Intergovernmental Panel on Climate Change echoes this view. In addition to rapidly reducing emissions, the team estimates that we will need to remove and sequester about 10 billion tons of carbon dioxide from the atmosphere each year by 2050, and that number will double by the end of the century. Today, there are about 2,000 square kilometers of seaweed farms in the world; According to a report by the National Academy of Sciences, Engineering, and Medicine, it takes 73,000 square kilometers to sequester 010 million tons of carbon per year, equivalent to planting a strip of seaweed farms nearly half a kilometer wide along the entire U.S. coastline.

If feasible, using seaweed to absorb carbon would be an elegant solution. In total, seaweed forests cover about 2 million square kilometers and absorb the equivalent of the Amazon rainforest. But most of the mothballs were short-lived. When seaweed is harvested, eaten by animals, or washed ashore, its stored carbon is released back into the atmosphere.

At least in theory, Running Tide's model would absorb the sequestered carbon and sink it to the ocean floor, where it would remain for centuries in cold, dark conditions, slowly decomposing. But tracking its fate will be difficult.

In Cobskok Bay, Maine, Severine vonchana welcomes seaweed foraging at Reverse Falls.

Left: Bladerwrak seaweed found at Reversing FallsRight: Vonchana welcomes diving to collect seaweed samples.

Scientists aren't entirely sure how much carbon seaweed removes from the atmosphere, as it depends on location and weather. It's also hard to measure exactly how much seaweed is wrapped around the bottom of the deep ocean rather than drifting elsewhere. In addition, there are key questions about the impact of growing large amounts of seaweed or sinking it to the bottom of the ocean to the marine ecosystem.

Put the cart before the horse?

Over the past few years, Running Tide and other seaweed-based carbon dioxide removal projects have gained traction for their leading. The MIT Technology Review published a pair of critical articles. And the scientists wrote in a diary in the Aquatic Science and Aquaculture Review last year: "There is no need for another yet proven technology-driven approach to climate change mitigation that has no sound scientific and market basis and would distract attention from other, more effective actions, such as reducing dependence on fossil fuels."

A rushing tide large seaweed hatchery in Braunschweig, Maine, where red algae fill the tank.

Another editor of some of the field's foremost scientists argues that the risk of seaweed subsidence "exceeds even perfunctory assessments of environmental impacts and social benefits." ”

To build trust, Running Tide is working with an independent scientific advisory board and an audit firm. It recently published a document detailing how it would explain how much carbon it had reduced. Davis, who reviewed the paper, said it was a good start, but it was "a very generalized process that requires more detailed explanation before it can be put into action." ”

Technician Danny Chea inspects the pH and temperature of algae at a running tidal macroalgae hatchery.

Odrin said he takes the criticism seriously but sees no reason to wait until all issues are resolved. "We don't have time to spend 15 to 30 years answering questions that we can only really answer if we actually go out and do these things," he said.

"There is an antithesis to the precautionary principle, and that is the responsibility to intervene," he said.

Time is of the essence

In a series of seaweed studies, Davis is part of a team that recently modeled the costs and potential climate benefits of seaweed — the most cost-effective way to reduce emissions. The researchers found that sinking seaweed to sequester carbon was much more expensive than replacing certain high-emission foods, such as soybeans linked to deforestation, with farmed seaweed.

Nonetheless, the researchers cited a range of potential challenges for seaweed as a climate solution, including the high cost of seaweed-based carbon removal, potential ecosystem disruption, and the uncertainty of a huge market for seaweed products. "As a result, prospects for a large-scale expansion of seaweed's climate benefits are very vague," they wrote.

"It's unrealistic to talk about seaweed quantities, at least not in the near future," Davis said.

A seagrass field worker is looking for seagrass organization. In September and October, new seaweed begins to form from the source.

Xi'er Price, a senior research scientist at Bigelow's Marine Science Laboratory who is studying how to use seaweed to mitigate climate change, said the idea that algae has only two options — "sink or use" — may be oversimplified. If farms place worn and broken seaweed leaf tips and tough holders attached to ropes close to shore in the most suitable places to sequester carbon in sediment, it may be possible to produce seaweed products and earn carbon credits. In this way, carbon capture and environmental impacts can be monitored directly, which is difficult, if not impossible, on the seabed.

Price believes that some key knowledge gaps will be filled in the next five years.

"At this point, the race is really not about which path is the best. "It's about which route is the fastest and cheapest," she says. I think now, we have to choose the fastest way. ”