HALIFAX, Nova Scotia (AP) — From the grounds of a gas-fired power plant on the eastern shores of Canada, a little-known company is pumping a slurry of minerals into the ocean in the name of stopping climate change. Whether it’s pollution or a silver bullet that will save the planet may depend on whom you ask.
From shore, a pipe releases a mixture of water and magnesium oxide — a powdery white mineral used in everything from construction to heartburn pills that Planetary Technologies, based in Nova Scotia, is betting will absorb more planet-warming gases into the sea. “Restore the climate. Heal the ocean,” reads the motto stamped on a shipping container nearby.
Planetary is part of a growing industry racing to engineer a solution to global warming using the absorbent power of the oceans. It is backed by $1 million from Elon Musk’s foundation, competing for a prize of $50 million more. Dozens of other companies and academic groups are pitching the same theory: that sinking rocks, nutrients, crop waste, or seaweed in the ocean could lock away climate-warming carbon dioxide for centuries or more.
Nearly 50 field trials have taken place in the past four years, with startups raising hundreds of millions in early funds for ocean carbon capture. However, the field remains rife with debate over the consequences for the oceans if the strategies are deployed at a large scale, and over the exact benefits for the climate.
Critics warn that efforts are moving too quickly and with too few guardrails. “It’s like the Wild West. Everybody is on the bandwagon, everybody wants to do something,” said Adina Paytan, who teaches earth and ocean science at the University of California, Santa Cruz.
Planetary, like most ocean startups, is financing its work by selling carbon credits — tokens representing one metric ton of carbon dioxide removed from the air. Largely unregulated and widely debated, carbon credits have become popular this century as a way for companies to purchase offsets rather than reduce emissions themselves. Most credits are priced at several hundred dollars apiece. The industry sold more than 340,000 marine carbon credits last year, up from just 2,000 credits four years ago, according to the tracking site CDR.fyi.
But that amount of carbon removal is a tiny fraction of what scientists say will be required to keep the planet livable for centuries to come. Those leading the efforts, including Will Burt, Planetary’s chief ocean scientist, acknowledge they’re entering uncharted territory — but say the bigger danger for the planet and the oceans is not moving quickly enough. “We need to understand if it’s going to work or not. The faster we do, the better.”
Efforts to capture carbon dioxide have exploded in recent years. Most climate models show that cutting emissions won’t be enough to curb global warming, according to the United Nations’ Intergovernmental Panel on Climate Change. The world needs to actively remove heat-trapping gases, as well — and the ocean could be a logical place to capture them.
While many strategies on land are limited by space and could impact nearby communities, the ocean regulates Earth’s climate by absorbing heat and carbon. By comparison, it seems limitless. “Is that huge surface area an option to help us deal with and mitigate the worst effects of climate change?” asked Adam Subhas, leading a carbon removal project with the Woods Hole Oceanographic Institution.
On a Tuesday afternoon along the edge of Halifax Harbour, Burt stashed his bike helmet and donned a hard hat to give two engineering students a tour of Planetary’s site. A detached truck trailer sat in a clearing, stocked with massive bags of magnesium oxide mined in Spain and shipped across the Atlantic to Canada. Most companies looking offshore for climate solutions aim to reduce or transform the carbon dioxide stored in the ocean.
If they can achieve that, Burt said, the oceans will act “like a vacuum” to absorb more gases from the air. Planetary is using magnesium oxide to create that vacuum. When dissolved into seawater, it transforms carbon dioxide from a gas to stable molecules that won’t interact with the atmosphere for thousands of years. Limestone, olivine, and other alkaline rocks have the same effect. Other companies are focusing on growing seaweed and algae to capture the gas. These marine organisms act like plants on land, absorbing carbon dioxide from the ocean just as trees do from the air.
However, while Planetary’s work could sound like some “scary science experiment,” Burt maintains that the testing suggests magnesium oxide poses minimal risks to marine ecosystems, plankton, or fish. The mineral has long been used at water treatment plants and industrial facilities to de-acidify water. Halifax Harbour is just one location where Planetary aims to operate. The company has set up another site at a wastewater treatment plant in coastal Virginia and plans to begin testing in Vancouver later this year.
According to the National Academies of Sciences, Engineering, and Medicine, the industry needs to remove billions of tons of carbon dioxide per year by mid-century to meet climate goals established nearly a decade ago during the Paris climate agreement. “The whole point here is to mitigate against a rapidly accelerating climate crisis,” Burt said. “We have to act with safety and integrity, but we also have to act fast.”
While there’s enthusiasm in the industry, coastal communities aren’t always quick to jump on board. In North Carolina, a request to dump shiploads of olivine near the beachside town of Duck prompted questions that downsized the project by more than half. The company Vesta, formed in 2021, promotes the mineral as a tool to draw down carbon into the ocean and create mounds that buffer coastal towns from storm surges and waves. During the permitting process, officials at the state Wildlife Resources Commission, Division of Marine Fisheries, and U.S. Fish and Wildlife Service raised substantial concerns.
Concerns raised about Vesta's project included potential long-term impacts and unanswered questions about remediation plans. The agencies warned that olivine could smother the seafloor ecosystem and pose risks to sea turtles and Atlantic sturgeon. Vesta CEO Tom Green noted the company never expected its original application to be approved as written. “It’s more the start of a dialogue with regulators and the community,” he said.
The project proceeded last summer with a much smaller scope, a restoration plan, and more detailed requirements to monitor deep-water species. Eight thousand metric tons of olivine shipped from Norway have been submerged beneath North Carolina’s waves. Green recognizes public skepticism and stresses that Vesta’s goal is environmental preservation, not harm.
Fishing communities have opposed another climate initiative proposed by Subhas, generating significant conversation and debate. The Woods Hole project originally aimed to pour 66,000 gallons of sodium hydroxide solution into ocean waters near Cape Cod, later downsizing to less than 17,000 gallons, with federal approval still pending. The Environmental Protection Agency believes the project’s scientific merit outweighs the environmental risks and expects no “unacceptable impacts” on water quality or fishing.
Fifth-generation fisherman Jerry Leeman III questions the fate of marine life if harsh chemicals are introduced to the habitat. “Are you telling all the fishermen not to fish in this area while you’re doing this project? And who compensates these individuals for displacing everybody?”
Subhas’s team expects the chemical’s concentrations to last less than two minutes in the ocean before dilution and has agreed to delay or relocate the project if schools of fish or patches of fish eggs are spotted in surrounding waters. Sarah Schumann, who fishes commercially and advocates for “fishery friendly” climate action, notes that the issue is complicated, stating, “If I was actually trying to decide where I land on this issue, I’d be twisted in knots.”
In Cornwall, England, Planetary faced protests against another climate project. In April last year, more than a hundred people marched along a beach carrying signs like “Keep our sea chemical free.” Critics like Sue Sayer of a research group studying marine seals indicated that Planetary seemed unaware of local ecological concerns.
An erosion of trust surrounds these ocean carbon capture initiatives as questions abound regarding their long-term viability and effects. Planetary halted another proposal to pump 200 metric tons of minerals pending government recommendations. Moreover, it ensures that it won’t sell carbon credits from its past chemical release.
While the science is still evolving and uncertainty remains, companies are pressing forward. Planetary Technologies recently announced it had captured 1,000 metric tons of carbon in the ocean, alongside partners like Shopify and Stripe for its credits. "This ongoing dialogue and cautious optimism signal a crucial balancing act in addressing climate change while maintaining ecological integrity," concludes Burt as he reflects on this urgent and evolving narrative.
