If you’ve gone for a swim in the ocean lately and resurfaced looking more like Medusa, you might’ve noticed how much seaweed is floating on top of the water.
Another thing the earth has too much of: carbon dioxide. Global carbon emissions have increased steadily each decade since the 1960s and hit 36.6B tons in 2022.
Carbon sinks — natural processes that remove carbon from the atmosphere, such as the ocean or soil — are able to remove some carbon, but make an increasingly smaller dent as more is produced each year.
The only way to keep up? Sink more carbon.
That’s the idea that inspired Patricia Estridge and Mike Allen to found Seaweed Generation, a climate tech startup that uses robots to sink seaweed into the depths of the ocean.
As seaweed grows and photosynthesizes, it absorbs carbon dioxide from ocean water (which ocean water absorbs from the atmosphere). To remove that carbon from the atmosphere for a prolonged period, the biomass needs to be altered.
Estridge describes the robots — named AlgaRays to describe their manta-ray-like shapes — as “Roomba meets Pac-Man” devices that take sargassum in through a cavity on the surface, sink it down 200 meters into the ocean, and release it onto the seabed.
“The deep ocean is already the biggest carbon sink on the planet,” says Estridge. “What we’re doing is just speeding that up.”
The robots are solar powered, to prevent emitting any additional carbon, and are autonomous — though they are monitored and controlled remotely by a human operator, for now.
While for now the test models are smaller, the winged robots will ultimately measure 32 feet wide with four-foot openings, and will be able to hold 16 tons of sargassum.
The robots will aim to intercept and sink sargassum before it reaches beaches and washes up on shore, a process that can cause even more issues for seafront communities that rely on tourism.
Seaweed Generation is currently completing a pilot project in Antigua to test out the functionality of its robots, and has a second robot model in the works that would focus on ecological monitoring.
Estridge says that in the short term, her team is aiming to have 10 seaweed-sinking robots in the oceans, and ultimately needs around 1k robots to eliminate the sargassum altogether.
“It’s not that many if you think about how many yachts there are in the Caribbean,” says Estridge.
While the company currently is accepting contributions through its site to build its robots, Estridge says it will one day have a commercial side to the business to be able to scale effectively.
Commercial cultivation of seaweed is already used in many parts of the world for food supply and as a thickening agent in many widely used home products, but also has applications in animal feed and fertilizer industries, two fields Estridge says would likely come next for Seaweed Generation.
Using robots to plant, grow, and harvest seaweed commercially would require fewer laborers to be put in dangerous ocean environments, and would stop carbon emissions that come from large vessels at sea.
Estridge notes that she didn’t devote her work to seaweed just for the love of slimy stuff, but instead because it can be such a valuable tool to fight climate change.
“I’m not necessarily passionate about sinking seaweed. I’m passionate about using seaweed for the best possible use case,” she says. “Sargassum is an opportunity to remove billions of tons of carbon dioxide every year.”