From the coast of Halifax Harbour, Planetary Technologies has staked its climate pitch on an industrial-sounding process: pumping a slurry of minerals into seawater to change how carbon dioxide behaves in the ocean, potentially trapping it for long periods. The company, based in Nova Scotia, frames the work as “Restore the climate. Heal the ocean,” and positions its tests as part of a wider push to use the ocean’s chemistry and scale as an emissions “solution.”
Planetary is among a fast-growing group of startups and academic teams exploring ways to engineer carbon removal in marine settings. AP reported that Planetary has been backed by $1 million from Elon Musk’s foundation and has also competed for a prize of $50 million tied to ocean and climate work. The industry’s investors and backers, in turn, have helped fund dozens of ocean-based projects, along with a market for credits that translates removal claims into tradable tokens.
In Planetary’s Halifax-area testing, a pipe releases a mixture of water and magnesium oxide, a mineral that is used in many products on land. Will Burt, the company’s chief ocean scientist, told AP that when the mineral is dissolved into seawater, it transforms carbon dioxide from a gas into stable molecules that do not interact with the atmosphere for thousands of years. Burt also described the basic mechanism as one that can make the ocean function “like a vacuum” that draws in additional gases, and he said the company’s testing so far suggests magnesium oxide poses minimal risks to marine ecosystems such as plankton or fish.
Planetary’s model is part of a broader menu of ocean carbon-removal approaches. Some projects aim to alter carbon chemistry so stored carbon does not readily return to the atmosphere, while others focus on biology—growing seaweed or algae—or on sinking organic material into deeper waters. AP reported examples including a company called Gigablue that has poured nutrients into New Zealand waters to grow phytoplankton, as well as projects that sink wood chips off Iceland or aim to sink Sargassum to extreme depths. In the Gulf of Mexico, another effort described by AP involves preparing to place sugarcane pulp on the seafloor, under a federal permitting process.
Despite the momentum, scientists and regulators say the work remains riddled with unknowns, particularly at the scale needed to matter for climate goals. Adina Paytan, an earth and ocean science professor at the University of California, Santa Cruz, said the sector resembles “the Wild West,” with “everybody” rushing into the arena and moving faster than safeguards can keep up. The tension reflects not only technical uncertainty—such as whether carbon removal will last—but also the risks of scaling up strategies that work in small trials to open-water operations.
A central feature of the industry’s expansion is carbon credits. Planetary and many other ocean startups, AP reported, finance work by selling carbon credits, which represent one metric ton of carbon dioxide removed. These credits are widely debated and have largely operated with limited regulation; most credits sell for several hundred dollars per token, according to AP’s description. AP also said CDR.fyi, a tracking site, shows marine carbon-credit sales rising dramatically in recent years, although the amount removed still represents a small fraction of what scientists say is needed to keep the planet livable over long periods.
The industry’s challenges show up not just in science labs but in permitting and community meetings. In North Carolina, AP reported that a request to dump shiploads of olivine near Duck prompted questions that cut the project scope by more than half. During permitting, agencies including the U.S. Fish and Wildlife Service cited concerns in writing about the potential for long-term impacts and possible harm to seafloor ecosystems and sea turtles and Atlantic sturgeon. In response, Vesta said it understood the process would be a dialogue with regulators and the community and the project proceeded last summer with a smaller scope and added restoration and monitoring requirements, with millions of tons of mineral shipped described by AP as already submerged.
Other ocean projects have also met sustained scrutiny from fishermen and coastal residents. AP reported that in Cape Cod waters, a climate project led by Adam Subhas of the Woods Hole Oceanographic Institution generated months of debate. The project proposed using sodium hydroxide solution, later downsized to use less than one-fifth of the originally proposed amount, with federal approval still pending. In discussions and reviews, the Environmental Protection Agency said it believed the scientific merit outweighed environmental risks and did not foresee “unacceptable impacts” on water quality or fishing, while fishermen raised questions about what would happen to eggs and whether anyone would compensate people for displaced fishing during testing.
In England, protests also followed Planetary’s plans described by AP. AP said more than a hundred people marched in April carrying signs reading “Keep our sea chemical free,” and cited local researchers who said they were surprised by the company’s initial understanding of which species live in St. Ives Bay. Separately, David Santillo of Greenpeace Research Laboratories at the University of Exeter took issue with Planetary’s baseline measurements, saying the company’s baseline in Cornwall was drawn from just a few days, which he argued made it difficult to detect effects reliably.
The field’s advocates say urgency is part of the problem, not an excuse for cutting corners. AP reported that while some oceanographers and industry supporters said it is time for ocean-scale tests, they also acknowledged that a dynamic ocean makes tracking outcomes difficult—materials can sink, dilute, or move. Scientists cited by AP emphasized the limits of observation and measurement, along with the need for modeling to simulate what would happen without interventions. Questions also linger about how long any carbon capture would remain locked away, including for biological or organic approaches where decomposition could potentially release carbon back to the atmosphere.
Even proponents who support trials are often cautious about what ocean removal could achieve if expanded rapidly. Ocean removal could require large, steady inputs of minerals or nutrients, plus energy and logistics for mining and shipping, and some efforts described by AP involve assumptions about massive areas of coastline for seaweed growth. David Ho of the University of Hawaii at Manoa, co-founder and chief science officer of the nonprofit [C]Worthy, said the question becomes what happens when such approaches scale to billions of tons every year, and that the outcome is still to be determined.
AP reported that Planetary has already begun monetizing results in measurable terms. Late last year, Planetary announced its Nova Scotia project captured 138 metric tons of carbon, allowing it to deliver exactly 138 carbon credits to early investors including Shopify and Stripe. The company said in February that it had sequestered a total of 1,000 metric tons of carbon in the ocean, and AP reported that other companies have signed deals for credits and begun additional projects, including efforts that involve electricity to alter seawater molecules.
For researchers watching the sector, a key worry is that markets may reward uncertainty before it is resolved. Paytan told AP she sees value in research but said carbon credits can open “doors for abuse of the system,” and Ho said that without more government-funded research, companies may have little way to advance besides selling credits. Still, Planetary’s Burt said he understood unease around selling credits and described a need to operate openly and responsibly while also moving faster than academia can.
The company and many in the field argue that the alternative to trying may be continued warming. Burt told AP that “We need to act with safety and integrity, but we also have to act fast,” and said studying ocean removal cannot happen at the same pace as scientists have studied the problems. With climate change pressures rising and the ocean-scale tests still in their early stages, the sector’s next steps—both scientific and regulatory—may determine whether ocean carbon removal becomes a proven tool or remains a controversial bet.