Aboard a World War II Navy barge bristling with metal cages, tanks, and an orderly maze of pipes and wires tied up in the Port of Los Angeles, a group of scientists is on a quest to answer a simple question: is there a way to coax the ocean into swallowing more carbon dioxide? The answer could hold the key to a cooler future.
The world’s oceans already act as a vast carbon sink, offsetting approximately one-quarter of the CO2 emissions that human activity generates each year. But as they face challenges like acidification and rising temperatures, they’re becoming less effective at taking up the planet-warming gas.
Engineers at Captura, a startup spun out from the California Institute of Technology, have devised a process that’s meant to revive that drawdown. Working like a large-scale desalination plant, it takes in ocean water, keeps a tiny portion aside, and zaps it with electricity using a special machine. The electrical charge splits the water into two parts: one acidic and the other alkaline.
The acid part goes into the remaining onboard ocean water, where it triggers a reaction causing CO2 to bubble out into storage tanks. The alkaline part is then added back to the seawater to neutralize the acidity before it is returned to the ocean, ready to absorb the same amount of CO2 that was removed.
“What we do is basically removing carbon dioxide from the seawater and then returning the decarbonated water to the ocean so it can suck more of the greenhouse gas out of the air,” says Captura’s CEO Steve Oldham. “It’s like wringing out a sponge to boost its absorption power.”
The power of the ocean
Captura is part of a small yet expanding cohort of companies including California startups Equatic and Calcarea, as well as the Dutch venture SeaO2, seeking to harness the power of the ocean to naturally concentrate CO2.
In addition to phasing out fossil fuels, climate science experts are increasingly convinced that vast quantities of CO2 will need to be taken away from the atmosphere in order to avoid runaway climate change. The notion is contentious, as removing CO2 on a large scale hasn’t been fully tested; a recent U.N. panel labeled the approach “unproven.”
But with millions of dollars in venture capital funding and lucrative contracts to offset the emissions of some of the world’s biggest companies, these firms are trying to prove otherwise.
An aerial view of the Captura barge at the Port of Los Angeles this past May. Crews are monitoring equipment pulling carbon dioxide (CO2) from seawater and onto a barge where a portion of CO2 is removed.
Photograph by Allen J. Schaben, Los Angeles Times/Getty Images
Pulling CO2 out from the ocean, where it is present at a concentration 150 times as high as in the atmosphere, is more efficient than capturing it from the air, where it makes up less than 0.05 percent of the total volume, believes Edward Sanders, COO of Equatic, which also runs a test vessel in the Port of Los Angeles.
He says that the technology also avoids using land, and systems can be integrated with desalination plants, wastewater treatment facilities, and other water-processing facilities and even coupled with offshore wind energy to facilitate access to oceanic storage sites.
According to Oldham, leveraging the ocean’s carbon-sucking power also doesn’t require building expensive machinery to interact with the air, ultimately helping reduce overall costs. “The ocean really does all the work itself,” he says.
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Both Captura and Equatic are confident that they will be able to pull CO2 for less than $100 a ton by the end of the decade—a significantly lower cost compared to direct air capture, which currently ranges between $250–600 per ton and is not anticipated to decrease anytime soon.
Uncharted territory
After almost a year of testing with the barge, which is designed to capture 100 tons of CO2 per year, Captura is expanding its operations by building a 1,000-ton-per-year facility in Norway. Equatic is also stepping up, establishing an even larger 3650-ton-per-year plant in Singapore. Both are set to be up and running by next year.
Companies say data collected there and at the Port of Los Angeles will help in the design of large-scale commercial facilities that sequester millions of tons of carbon annually.
But even hitting that target would be just a drop in the bucket. The IPCC estimates up to 12 gigatons of CO2, or about a quarter of the current global annual emissions, would need to be removed from the air every year to make a meaningful dent in the carbon debt.
To facilitate this, Captura, Equatic, and the others must erect thousands of new facilities that extract CO2 from seawater around the world. That buildout would entail billions of dollars in capital investment. More importantly, it would take massive quantities of carbon-free energy to power decarbonization plants.
Critics argue these resources would be better spent reducing fossil fuel use and electrifying the economy. “Removing already-emitted carbon is laughably small, incredibly expensive, and full of engineering obstacles,” says Jonathan Foley, executive director of Project Drawdown, a nonprofit organization focused on climate solutions. “Limited research on this should continue, but our time and resources should focus on cutting emissions as quickly as possible.”
Sanders points out that Equatic’s process yields green hydrogen as a byproduct, which can be used to partially power the process and cut the net power requirement. He notes that further energy efficiency could be achieved by tapping energy during off-peak times – typically late at night or early in the morning – when demand is lower and costs are reduced.
Questions also remain about the environmental impact of the technology. Lisa Levin, a marine ecologist at UC San Diego’s Scripps Institution of Oceanography, warns that processing huge volumes of seawater could have unforeseen consequences on ocean ecosystems.
“We’re in uncharted territory here,” she says. “Nobody knows what’s going to happen when you manipulate the ocean chemistry at such a large scale.”
Levin claims that there are risks to marine life as well. “Whenever large volumes of water are drawn in, they bring along everything within it—including plankton, fish larvae, and other small animals,” she explains.
Sanders says the Equatic’s process is designed to have minimal impact on the local ecosystem, adding that the company has commissioned an environmental impact assessment to understand the potential implications of implementing the technology at scale. “We do not want to cause greater harm to the planet in the process,” he maintains.
Oldham echoes the sentiment, stressing that Captura’s process does not add anything to ocean waters that’s not already there. “We won’t risk disrupting the ocean with things we haven’t fully understood,” he asserts. “We simply can’t afford it.”
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