The ocean is already the planet’s most powerful carbon removal tool. But we need it (or something else) to do more to reach net zero emissions. This startup thinks it has the solution: pulling seawater from the ocean and zapping it to remove and store carbon.
Over the coming months, the pilot project on the barge will suck up a backyard swimming pool worth of ocean a day, passing it through the big blue-gray boxes that house devices called flow electrolyzers. An electrochemical process causes calcium carbonate, a solid limestone-like material, to precipitate from the seawater and entrap the liquid CO2. The decarbonised seawater is then infused with CO2 drawn from the atmosphere and returned to the ocean with the same chemical composition as before. That, says Gaurav Sant, director of UCLA’s Institute for Carbon Management, allows for a precise accounting of the CO2 removed while eliminating possible adverse environmental impacts on the ocean. SeaChange also produces green hydrogen as a byproduct, which can be used to power the process.
“What we learn from these systems will then inform the design and the scale-up of the technology,” said Sant at the mid-April unveiling of the pilot project. “It will go into plants that process thousands of tons of carbon dioxide a year, and then it will be in commercial-scale plants that are doing millions of tons of carbon dioxide.”
The researchers project that SeaChange could pull around 10 pounds (4.6 kilograms) of CO2 from the atmosphere per metric ton of seawater processed, which is equivalent to the average tailpipe emissions of a car driven 12 miles (19 kilometres). The pilot project is designed to process more than 50 metric tons a day during the trial, according to the researchers. Sequestering 1 metric ton of carbon dioxide requires processing 220 metric tons of seawater. During the process, SeaChange also produces about 75 pounds (35 kilograms) of hydrogen. Sant and his colleagues are aiming to sequester CO2 for less than $100 per metric ton, a price that’s become a kind of Holy Grail for carbon removal to be cost-effective.
To not only stop but reverse the rise of CO2 in the atmosphere will require removing gigatons — that is, billions of tons — of carbon dioxide from the air. Relying on the seas for such a wildly Herculean task could have unforeseen consequences for marine life, according to ocean scientists.
Over the course of 24 months, the SeaChange project has gone from a laboratory experiment to a working prototype plant. The UCLA researchers have spun off a startup called Equatic Inc. to commercialise the technology and sell carbon credits and hydrogen. Sant, a founder and co-leader of Equatic, declined to disclose the startup’s funding but noted that it “is very well funded, having raised many millions” of dollars.“They are moving very fast,” says Douglas Wicks, a program director at the US Department of Energy’s Advanced Research Projects Agency – Energy (ARPA-E), which awarded the scientists a $1 million grant in 2022.
Wicks says that when he first visited the UCLA lab last summer, the researchers showed him a credit card-sized SeaChange processing unit. When Wicks returned in September, it was book-sized, and then six months later, he was standing on the barge in Los Angeles. The group is also operating a second pilot project in Singapore.
“I’m just very impressed with their ability to scale,” Wicks says. “I have full expectations that they are going to meet their commercial deployment goals.”
That speed, however, could outstrip governments’ ability to effectively regulate large-scale ocean-based carbon dioxide removal projects that are attracting growing interest from investors, according to Romany Webb, deputy director of the Sabin Center for Climate Change Law at Columbia University. She notes that while a multitude of existing state, national and international laws could apply to such ventures, they may not be sufficient.
“We are going to need to think about legal frameworks for deploying these activities, and for ensuring that they occur in a way that maximizes their benefits and that minimizes the potential risks,” says Webb, an associate research scholar at Columbia Law School. She adds it’ll be crucial to develop procedures to verify the validity of carbon credits generated by commercial operators of ocean-based carbon dioxide removal projects (CDR).
Sant says Equatic’s pilot project in Los Angeles is operating under the conditions of a Vessel General Permit issued by the US Environmental Protection Agency that regulates the discharge of ballast water from commercial ships. Large-scale Equatic plants would likely be located on coastal land, though Sant says it might be possible to place them in the ocean near offshore wind farms that could supply electricity to the projects.
Despite Equatic’s success so far in scaling up SeaChange, it — like every CDR startup — remains a long way from proving its technology can work at a meaningful and cost-effective scale. Significant hurdles and questions also remain about the environmental impact of the technology.
The researchers called SeaChange’s energy demand “formidable” in a 2021 paper published in the journal ACS Sustainable Chemistry & Engineering. They estimated that to keep global temperature rise to 1.5C, the aspirational target set by the 2015 Paris Agreement, Equatic would need to sequester 10 gigatons of CO2 annually by 2050, or about a fourth of current emissions. (Other groups have come up with different estimates of how much carbon the world will need to remove from the atmosphere.) That would require a $1.4 trillion buildout of solar power stations to supply electricity to nearly 1,800 Equatic decarbonisation plants.
Sant says over the past two years Equatic has improved the technology’s energy efficiency and the plants would need less electricity than initially anticipated. The company now estimates it takes 2 megawatt hours of electricity to remove 1 metric ton of CO2. The hydrogen produced onsite could supply half that energy demand. (The average US home consumes slightly less than 1 megawatt-hour a month, according to the US Energy Information Administration.)
University of Hawaii oceanographer David Ho argues that the massive ramp-up in renewable energy needed to power ocean-based CDR on the scale Equatic advocates for would be better deployed to curtail fossil fuel use.
“We have to halve our emissions by the end of this decade, and that’s where the focus should be,” says Ho, who has started a nonprofit called [C]worthy to develop protocols to verify ocean carbon dioxide removal. “Unless we have unlimited renewable energy, it just doesn’t make sense to use it for something like this technology.”
Other ocean carbon-based CDR approaches involve fertilising the seas with iron to spur phytoplankton blooms, adding minerals to increase the ocean’s ability to absorb carbon or growing plantations of CO2-sequestering seaweed and then sinking the macroalgae to the seabed. Those proposals have raised concerns over the difficulty of quantifying and verifying CO2 removal, given the complexity of marine geochemistry, as well as fears over the unknown impact on ocean ecosystems.
Those risks have led to local opposition when other ocean-based CDR companies have proposed trial projects. Last month, more than 300 surfers, business owners, politicians and residents of the UK coastal community of Cornwall rallied on a beach to protest Canadian startup Planetary Technologies’ plan to add a chemical compound that reduces ocean alkalinity to a wastewater pipe that stretches into St. Ives Bay.
The UCLA researchers designed SeaChange to sidestep those issues. “Our process can ensure that we have both carbon sequestration, but also no negative addition or subtraction from the seawater that we take in to ensure that we have minimal effect or no effect on the local ecosystem,” says Dante Simonetti, an associate professor of chemical and biomolecular engineering at UCLA and a cofounder and head of technology at Equatic.
SeaChange’s potential impact on marine life, though, has not yet been studied. “We have commissioned a detailed environmental impact assessment to understand the implications of implementing our technology at scale,” says Sant.
At the breadth needed to have a beneficial impact on the climate, the technology will produce millions of tons of calcium carbonate particulate matter, according to a 2023 paper co-authored by Sant.
Lisa Levin, a marine ecologist at the Scripps Institution of Oceanography at the University of California at San Diego, says that could have an adverse impact on the ocean.
“The danger of those particles are that they affect light penetration and animals easily could mistake them for food and eat them,” says Levin, lead author of a March paper published in the journal Science that examined potential deep sea impacts of ocean-based CDR. “If they actually fell to the seafloor, then they form a layer of sediment that could damage whatever is on the bottom.”
Sant says ocean currents would rapidly disperse calcium carbonate particulate to prevent it from accumulating in one place and clouding the water.
The huge volumes of seawater Equatic plants would process could also pose a threat to marine life, according to Levin. Sequestering 10 gigatons of carbon dioxide annually would require processing 3,500 gigatons of seawater, according to the 2021 paper. “Whenever you draw in a lot of water, you draw in all the things in the water, including the small animals, plankton, invertebrate larvae, [and] fish larvae,” says Levin. Locating Equatic installations at desalination plants and other industrial facilities that already take in large quantities of ocean water could reduce that impact, she notes.
“This is a scale of industrialisation that we’ve never actually accomplished before,” says Sant. “And so the success of these technologies is not only in the technologies themselves, but also in how fast you can build them out.”
