Seaweed is mucking up beaches. This robot could stop it — and fight climate change


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Seaweed Generation’s marine biologist Duncan Smallman at the company’s workshop in Glasgow, Scotland.

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Seaweed Generation’s marine biologist Duncan Smallman at the company’s workshop in Glasgow, Scotland.

Robert Ormerod for NPR

On a rainy September morning, on the outskirts of Glasgow, Scotland, a handful of engineers are standing around a plastic swimming pool.

Sitting along the water’s surface are little rubber duckies, the kind you’d expect to find in a bathtub, not an engineering laboratory.

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But these ducks are an important part of what’s about to happen. They’re a floating target for a swimming robot, one that its creators are billing as a possible solution to threats against human health.

It doesn’t look like much yet — a chunky metal box with a camera on its head and a belly full of ballasts — but if all goes well today, it’ll get an upgrade and, eventually, a chance to swim the open ocean.


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Robotics engineer Oscar Brennan and mechanical engineer Vasileios Konstantaras lower a submersible into a pool to check the vehicle ahead of another test in a quarry robotics engineer.

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Robotics engineer Oscar Brennan and mechanical engineer Vasileios Konstantaras lower a submersible into a pool to check the vehicle ahead of another test in a quarry robotics engineer.

Robert Ormerod for NPR


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The Seaweed Generation submersible AlgaRay 2 in a pool at the company’s workshop in Glasgow, Scotland.

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The Seaweed Generation submersible AlgaRay 2 in a pool at the company’s workshop in Glasgow, Scotland.

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The ducks are just a stand-in for the robot’s eventual prey: A stinky seaweed, called sargassum, that keeps piling up on shores along the Caribbean and North Atlantic, wreaking havoc on local ecosystems and economies.

But if this robot can successfully tackle the seaweed, it may go on to help fight an even bigger bad guy: climate change.

This robot’s first foe is a 5,500-mile long blob of seaweed

Sargassum is technically a type of algae — a leafy, rootless, buoyant plant, which bunches up in islands and floats around the North Atlantic Ocean and Caribbean Sea.

For hundreds of years, humans have observed these patches of sargassum waxing and waning annually. They steadily increase in size and abundance in the spring, then disappear come winter.

But since 2011, the overall size and number of these blooms has ballooned.


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Seaweed at the Seaweed Generation workshop in Glasgow, Scotland.

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Seaweed at the Seaweed Generation workshop in Glasgow, Scotland.

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Meet the sargassum belt, a 5,000-mile-long snake of seaweed circling Florida

Environment

Meet the sargassum belt, a 5,000-mile-long snake of seaweed circling Florida

“The low point of the cycle is now higher than what the cycle’s high point was just five or six years ago,” according to Brian Barnes, who tracks sargassum with the University of South Florida using satellite imagery.

He said this year’s sargassum blooms formed a 5,500-mile-long, 10 million metric ton belt that snaked from West Africa to the Gulf of Mexico.

The cause of this growth is still a mystery to researchers. But out in the open ocean, the flourishing plant life doesn’t seem to be a problem. It even serves as a rich habitat for turtles, fish, crabs and birds.

But the more sargassum grows, the more some of it gets pushed closer to the coast by currents and trade winds. That’s when the threats to human life start to multiply.

The more we learn about sargassum, the more clearly it looks like a danger to coastal communities

In shallow waters, sargassum can smother coral reefs and alter the water’s pH balance, killing off local seagrasses and mangroves. It can choke boat motors, constricting local fishing yields if not cutting off whole marinas. Sargassum once clogged a desalination plant so badly that residents of the U.S. Virgin Islands were told the drinking water may not be safe.

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Water analysis samples at the Seaweed Generation workshop in Glasgow, Scotland.

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Water analysis samples at the Seaweed Generation workshop in Glasgow, Scotland.

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Detail of tanks at Seaweed Generation’s workshop in Glasgow, Scotland.

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Detail of tanks at Seaweed Generation’s workshop in Glasgow, Scotland.

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Once ashore, piles of sargassum pose a threat to any economy that relies on beaches and the tourists who come to access them. Cleaning up the sargassum with heavy equipment can cost millions and up the risk of shoreline erosion.

But leaving sargassum on the beach poses hazards to local residents. Sargassum starts to decay after a day or so, releasing hydrogen sulfide and the smell of rotten eggs.

Giant blobs of seaweed are hitting Florida. That's when the real problem begins

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Giant blobs of seaweed are hitting Florida. That’s when the real problem begins

Residents who are exposed to these gases year after year say they experience symptoms like headaches, nausea, rashes and trouble sleeping. During a particularly bad stretch of sargassum buildup in 2018, doctors on the islands of Guadeloupe and Martinique reported more than 8,000 cases of what they deemed “acute sargassum toxicity.”

And then there’s the question of where to take sargassum once it’s off the beach. A growing body of research suggests sargassum may contain heavy metals like arsenic, which it might leach into the groundwater if it were, say, disposed of or stored in a landfill.


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Seaweed cultivation tanks at the Seaweed Generation workshop in Glasgow, Scotland.

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Seaweed cultivation tanks at the Seaweed Generation workshop in Glasgow, Scotland.

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There’s a whole list of companies trying to repurpose sargassum into consumer goods like notebooks, shoes, soap bars and biodegradable plastic.

But these businesses struggle against an unpredictable sargassum supply and expensive transportation from beach to factory.

Plus, there’s a gap between supply and demand — sargassum is overwhelming some Caribbean beaches, but there’s not an overwhelming demand for, say, sargassum soap.

This is where the AlgaRay comes in

The U.K.-based startup Seaweed Generation thinks it has an elegant solution to stem all these intersecting challenges: A solar-powered, autonomous robot called the AlgaRay.

The idea is that the AlgaRay would intercept patches of sargassum heading toward the shore, drag them back into the open ocean, then submerge them down to depths of about 150 to 200 meters. At that point, the air pods that keep sargassum afloat would pop and the plant would slowly keep sinking.


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Mechanical engineer Vasileios Konstantaras and robotics engineer Oscar Brennan test the company’s submersible.

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Mechanical engineer Vasileios Konstantaras and robotics engineer Oscar Brennan test the company’s submersible.

Robert Ormerod for NPR


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The Seaweed Generation submersible AlgaRay 2 in a pool at the company’s workshop in Glasgow, Scotland.

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The Seaweed Generation submersible AlgaRay 2 in a pool at the company’s workshop in Glasgow, Scotland.

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“It’s kind of like a Pac-Man meets the Roomba,” says Paddy Estridge, the company’s CEO and co-founder.

In the short-term, such a robot could help coastal communities keep the beaches clear.

But to help fund this work, Seaweed Generation is also marketing the AlgaRay as a way to develop a technology that could one day fight back against climate change.

“What the AlgaRay is for us is the key to unlocking a huge economy of carbon removal and reductions using seaweed,” Estridge said.

Estridge, whose background is in software engineering, started researching climate solutions after moving to California for a job with Google and finding herself under a frequent haze of wildfire smoke.

Like many people in the climate space, she believes the world won’t be able to rein in its greenhouse gas emissions quickly enough to limit warming to 1.5 degrees celsius above pre-industrial levels, which, in turn, would avoid the most catastrophic impacts of climate change.

So she’s interested in another route — removing the carbon dioxide from the atmosphere. And she thinks she’s found a good tool to do the work.


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Seaweed Generation co-founder Patricia Estridge at the company’s workshop in Glasgow, Scotland.

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Seaweed Generation co-founder Patricia Estridge at the company’s workshop in Glasgow, Scotland.

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“Seaweed is amazing,” she told NPR. “It grows quickly in the ocean. You don’t need fertilizer, you don’t need any fresh water.” And since it’s a plant, it naturally removes carbon from the air using photosynthesis.

Sinking seaweed to capture the carbon it holds is gaining popularity. And it makes sense as a concept, according to researchers like Columbia University’s Ajit Subramaniam.

“As you go deeper and deeper, it takes longer and longer for the carbon to make it back up to the atmosphere,” Subramaniam told NPR. “Our current models of ocean circulation basically tell us that if you go below about 2,000 meters, then you are not going to come back to the atmosphere for at least 100 years.”

But the logistics are more complicated. In order for sunken sargassum to translate into legitimate carbon removal, the AlgaRay would still need to pass two big tests.

Before the climate-fighting can happen, the technology has to work

The first test is scalability — could the AlgaRay do enough to make a meaningful difference?

Seaweed Generation says that one AlgaRay, working 12 hours every day for three months of the year, could alone sink about 80,000 metric tons of sargassum annually.


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Seaweed Generation marine biologist Duncan Smallman tests the submersible AlgaRay 2 at a quarry in Scotland.

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Seaweed Generation marine biologist Duncan Smallman tests the submersible AlgaRay 2 at a quarry in Scotland.

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The Seaweed Generation team prepares to test the submersible AlgaRay 2 at a quarry in Scotland.

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The Seaweed Generation team prepares to test the submersible AlgaRay 2 at a quarry in Scotland.

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Assuming it was taking all that sargassum to deep enough waters, that’d translate into 8,000 metric tons of carbon removed.

It’s not bad for one little robot. The first direct carbon capture facility in Iceland, which is still being built, currently vacuums up 4,000 metric tons of carbon dioxide from the air each year.

But, at the end of the day, the AlgaRay would sequester just a tiny fraction — .0002% — of the carbon dioxide that humans emit annually by burning fossil fuels.

Seaweed Generation could scale up the number of AlgaRays in use and start sinking more of the sargassum that blooms in the open ocean each year.

But that might start to clash with the second test, which is what climate minds call “additionality” — to be helpful carbon removal, the AlgaRay would need to sink carbon that wouldn’t naturally sink on its own.


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The Seaweed Generation submersible AlgaRay 2 is tested at a quarry in Scotland.

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The Seaweed Generation submersible AlgaRay 2 is tested at a quarry in Scotland.

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And since these massive monster sargassum blooms are a relatively recent phenomenon, researchers like Subramaniam say that more studies are needed to understand just how much of sargassum in the open ocean sinks before it decays on the surface.

There’s also the question of what would happen to marine life, both in the upper and deeper ocean, if we started sinking sargassum, or any kind of biomass, en masse.

Seaweed Generation is clear-eyed about these unknowns. But they’re also determined to start the work of carefully collecting the answers rather than wait around for someone else to sort them out.

“I think it’s really important to think about the problem that’s right in front of you,” Estridge said. “If you zoom too far out, you get really, really overwhelmed. But if you focus on that next step, you can make some progress.”

The same could be said for the AlgaRay.


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The Seaweed Generation team prepares to test the submersible AlgaRay 2 at a quarry in Scotland.

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The Seaweed Generation team prepares to test the submersible AlgaRay 2 at a quarry in Scotland.

Robert Ormerod for NPR


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The Seaweed Generation submersible AlgaRay 2 is tested at a quarry in Scotland.

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The Seaweed Generation submersible AlgaRay 2 is tested at a quarry in Scotland.

Robert Ormerod for NPR

Back in the lab in Scotland, the engineers are putting it through a series of tests: Turning on its headlight, trying out its thrusters, ensuring it’s recording all the data needed to assess its own performance.

Estridge estimates it may be another 18 months until the AlgaRay could be ready to operate autonomously in the wild. But for now, it’s checking all the boxes, scooping up each rubber duckie one by one.

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The audio version of this story was produced by Berly McCoy. It was edited by Rebecca Ramirez and Andrea Kissack. Emily Olson checked the facts. Robert Rodriguez was the audio engineer.