Startups turning to the ocean to capture more carbon off Southern California’s coast

Picture a can of Coke.

When you first pop the top, carbon dioxide pumped into the sugary liquid delivers that beloved effervescent fizz. But soon, the soda starts to go flat. That’s because gases tend to move from areas of high to low concentration. And since our atmosphere is only 0.04% carbon, the concentrated carbon dioxide in the Coke will bubble out until it’s more balanced with the non-effervescent air around it.

The process also works in reverse. If the liquid has less carbon than the air, it’ll draw carbon from the atmosphere.

That principle is the basis for a nascent industry bubbling up in Southern California that aims to use the ocean itself as a tool to fight climate change.

To date, most proposals to remove carbon from the atmosphere have focused on trying to scrub the greenhouse gas directly from the air. But that form of carbon capture is proving to be a pricey and underperforming endeavor, prompting pushback from environmental groups. So some interest and funding is now pivoting to a process known as direct ocean carbon capture, where technology is used to remove carbon from the ocean so it will naturally pull more carbon out of the air.

Thanks to recent infusions of public and private dollars, two local startups are testing different ocean carbon capture systems off the coasts of Orange and Los Angeles counties. Each hopes to scale up the technology for commercial markets within the next few years, which advocates say could slow global warming that’s already raising sea levels, triggering more intense weather patterns and posing other challenges around the globe.

“It’s huge. It’s existing. It’s free of charge. It’s already built,” Steve Oldham, CEO of Captura, which is running a pilot test off Newport Beach, said of the sea.

“So it’s a very powerful method, we think, of removing CO2 from the atmosphere.”

Steve Oldham, CEO of Captura, right; with Eric Marks, mechanical engineer, left; Fenfang Wu, lead pilot engineer and lab manager; and Maya Kashapov, with business development at their laboratory in Pasadena, CA, on Wednesday, February 15, 2023. (Photo by Jeff Gritchen, Orange County Register/SCNG)

Lots of questions remain, from the cost and scalability of the technology to where the carbon will go and how it will get there. That’s why Victoria Bogdan Tejeda, an environmental attorney with the Center for Biological Diversity, said she has serious concerns about the safety and viability of such technologies.

The debate boils down to a fundamental disagreement over a question that’s dividing even some of the most ardent green energy supporters.

If you believe — as Oldham, the U.S. Department of Energy and some researchers do — that we won’t be able to keep the planet from reaching the 1.5 degree Celsius spike identified as a key turning point for worsening impacts from global warming simply by reducing emissions alone, then projects like these are well worth exploring.

“We can be more efficient with fossil fuel usage. We cannot completely stop using it,” said Dante Simonetti, a chemical and biomolecular engineering professor at UCLA who is helping to spearhead ocean carbon capture pilot programs along the Los Angeles and Singapore coasts.

“We need every technology because every technology does indeed have benefits and downsides. That’s what makes the problems complex.”

But if you believe — as Tejeda, some major environmental organizations and other researchers do — that we can avoid the worst impacts of global warming by rapidly eliminating our reliance on fossil fuels while using trees, wetlands and other natural spaces to draw down residual greenhouse gases, then ventures like ocean carbon capture removal aren’t worth the risks and resources.

“It just seems like there are far too many questions,” Tejada said.

How does it work?

Direct ocean carbon capture operations look a bit like desalination or wastewater treatment plants, though something quite different is going on inside their systems of filters, tubes, pumps and tanks.

With Pasadena-based Captura, water is pulled from the surface of the ocean and passed through filters before it gets into the guts of the plant. A fraction of that water is diverted to flow through the company’s proprietary electrodialysis system, which was developed at CalTech by two professors who co-founded Captura in 2021. Their system uses a jolt of electricity (currently generated, in pilot projects, via solar power) to split the salt and water into an acid and an alkaline base. The acid is added to the original flow of ocean water, triggering a chemical process that extracts carbon dioxide and leaves acidic ocean water behind. The alkaline base then is used to neutralize the acidity, and that water is poured back into the ocean to absorb more carbon.

Other than scrubbing out carbon, which has been acidifying the ocean and leading to problems such as coral bleaching, Oldham said he’s confident their process doesn’t change the sea in ways that harm marine life. Fine-mesh filters prevent creatures from being pulled into the system on the front end, while the water coming out the other side is the same temperature, with no added absorbents or byproducts.

“Captura’s process adds nothing and takes nothing from the ocean,” he said.

Captura’s direct ocean carbon capture pilot project on the south side of Newport Harbor. The solar-powered project can remove 1 ton of carbon from the ocean each year. (Photo courtesy of Captura Corporation)

Membrane filters are part of Captura’s direct ocean carbon capture plant, which is under development at their laboratory in Pasadena, CA, on Wednesday, February 15, 2023. (Photo by Jeff Gritchen, Orange County Register/SCNG)

A carbon capture tank is part of Captura’s direct ocean carbon capture plant, which is under development at their laboratory in Pasadena, CA, on Wednesday, February 15, 2023. (Photo by Jeff Gritchen, Orange County Register/SCNG)

An electrodialysis system is part of Captura’s direct ocean carbon capture plant, which is under development at their laboratory in Pasadena, CA, on Wednesday, February 15, 2023. (Photo by Jeff Gritchen, Orange County Register/SCNG)



Captura launched its first pilot project on the shores of Newport Harbor in August, at CalTech’s Kerckhoff Marine Laboratory. That project, funded with founders’ seed money and $1 million won through Elon Musk’s XPRIZE Carbon Removal competition, can remove a ton of carbon from the atmosphere each year.

A system 100 times larger is nearing completion at the company’s headquarters in Pasadena through funding from Southern California Gas. Captura aims to launch that plant at an undisclosed location along the California coast by June. And the startup says $12 million recently raised from a half-dozen investors will pay for a third pilot program to  remove 1,000 tons of carbon from the air each year through the ocean.

Then there’s SeaChange, which grew out of UCLA’s Institute for Carbon Management. In April, the startup plans to launch its first pilot plants at AltaSea, in the Port of Los Angeles, and on the coast of Singapore. Each shore-side pilot will be capable of drawing more than 40 tons of carbon down from the air each year. The company’s financing includes a $1 million grant from the Department of Energy, $1.5 million from Volkswagen’s settlement over an emissions cheating scandal and a $21 million pledge from the Chan Zuckerberg Initiative.

SeaChange systems also use a jolt of electricity (currently generated by natural gas pulled from the grid) but applies it to all of the surface water pulled into their plants. The reaction causes minerals in the seawater to form solids, Simonetti explains, creating sand-like bits of limestone and brucite that lock carbon dioxide inside. The alkalized and decarbonized water is then released back into the ocean.

SeaChange’s process also creates pure hydrogen along the way, which it aims to capture and sell as a potential source of emissions-free energy.

Where does the carbon go?

When it comes to the carbon-containing solids created in SeaChange’s process, Simonetti said that material can be used to replenish sand on beaches or made into building materials such as cement. But much of it, he said, would likely be released back into the ocean.

As for the stream of pure carbon dioxide Captura’s process captures, it can either be sequestered underground (typically by injecting it into rock formations), or it could be used to make products such as plastics. Lots of ideas for such recycled carbon products are floating around, though most are still in the demonstration phase.

Captura also has a unique proposal for carbon sequestration that it believes could lower the price tag and speed the timeline for deploying its technology: put the plants on decommissioned offshore oil and gas platforms. That way, Oldham explained, the carbon could be sent back under the ocean floor for storage using the same permitted infrastructure that oil and gas companies installed to extract the fossil fuels that led to the carbon being in our atmosphere in the first place.

An artist’s rendering of an industrial-scale version of Captura’s ocean carbon capture technology at sea. (Photo courtesy of Captura Corporation)

That proposal raises flags for Tejeda, since she said she’s not aware of any good research on potential impacts or regulations that would permit that process. Also, she noted serious concerns about the reliability of aging offshore oil infrastructure. If companies start using those systems to inject carbon underground, would they then take responsibility for maintaining that equipment and liability if something goes wrong, such as a carbon leak that could prove disastrous for marine life? After all, while carbon dioxide occurs naturally in the environment at low concentrations, elevated levels can trigger headaches, confusion and heart issues, while high doses can lead to suffocation.

Asked about such concerns, Maya Kashapov, who oversees business development for Captura, noted their business model is to license their technology to partners who want to permit, build, operate and maintain the plants. But she said one of the reasons oil and gas platforms are appealing sites for these projects is because there are permits already in place “to ensure their continued use is done in a safe way in accordance with local regulations.”

With any other sort of sequestration plan, one of the biggest concerns Tejeda and other some other environmentalists always have is with how the carbon is transported.

Using trucks means burning fossil fuels to move the carbon around, plus it poses safety concerns in case of crashes. It’s not a great time to discuss using trains to transport hazardous materials, with the Ohio derailment top of mind. And when it comes to pipelines, environmental groups cite a disaster that happened three years ago in Mississippi, when a pipe carrying liquefied carbon dioxide ruptured. The nearby community of Satartia was blanketed in a plume of carbon that caused health problems, including breathing and stomach issues, that a Huffington Post investigation found lingered for many residents a year later.

The Satartia incident prompted the federal Department of Transportation’s Pipeline and Hazardous Materials Safety Administration to announce in May that it was updating safety standards for carbon dioxide pipelines. Those rules, and California guidelines for carbon capture and storage, are still under development.

“The energy industry has actually been managing and safely storing carbon dioxide within their oil and gas operations for decades, with millions of tons of CO2 successfully stored in geological sites worldwide,” Kashapov noted. And she said they have faith that regulators will have stringent oversight for these projects as the carbon sequestration industry takes off over the next decade.

Is it scalable?

If direct ocean carbon capture projects can overcome such hurdles, they still need to make the process much more cost effective than it is today. They’ll also have to scale up the technology so its big enough and fast enough to make a dent in global warming.

Even if all five pilot plants Captura and SeaChange are working on today were up and running, they’d only remove around 1,181 tons of carbon a year — about the equivalent of taking 236 cars off the road. But both startups say they’re confident they can quickly scale up to plants that could help the ocean draw down 1 million tons of carbon annually.

Around 37 billion tons of carbon are emitted globally each year. Oldham cites an estimate from the Intergovernmental Panel on Climate Change that says up to 30% of the world’s emissions “will have to be removed, rather than stopped,” leaving natural systems, such as forests, and manmade systems, such as carbon capture plants, to absorb at least 11 billion tons of carbon each year.

The SeaChange team estimates roughly 1,800 industrial-scale versions of its ocean carbon capture plants would sequester about 10 billion tons of carbon per year. Building that many plants would cost trillions of dollars. But if even a fraction of that total gets built, SeaChange says it could make a serious dent in the problem.

Theoretically, the plants could go anywhere. Ocean carbon capture systems aren’t nearly as finicky as, say, offshore wind or wave energy projects, with no particular weather patterns or ocean temperatures needed to make them viable. So Simonetti said they can set up shop wherever regulators and the community welcome them.

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While there’s some potential market for the carbon produced through ocean capture projects (and hydrogen, with SeaChange’s process), the main moneymaker here will be from companies willing — or forced — to pay to offset their own carbon production. Simonetti said that makes places like Singapore, which is pushing carbon taxes, attrative for these projects since the market already exists.

The Department of Energy has set a target for projects like these to reach a price of $100 per ton of removed carbon to make them viable.

Neither company shared how much their processes pencil out to now. But both acknowledged costs still need to come down signficantly, while also saying they’re confident they can get to a competitive price point soon.

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