A scene from the Sanibel Lighthouse on Friday, Aug. 9, 2024. The line where storm water runoff from various watersheds and the Gulf of Mexico meet can be seen behind them. Tropical Storm Debby came through the area earlier in the week. Pollutants and nutrients are often found in the runoff. Red drift algae is also present.
Halifax, Nova Scotia – On the eastern shores of Canada, a startup called Planetary Technologies is making waves—literally. From a gas-fired power plant site in Nova Scotia, the company is pumping a mixture of water and magnesium oxide into the ocean, claiming it can help slow climate change. Whether this is an innovative solution or an environmental gamble depends on who you ask.
Planetary is part of a fast-growing industry focused on using the ocean to absorb excess carbon dioxide. The company, backed by $1 million from Elon Musk’s foundation and competing for a $50 million prize, is betting that dissolving minerals into seawater will help the planet “breathe” better. Their motto, stamped on a shipping container at the site, reads: “Restore the climate. Heal the ocean.”
They’re not alone. In the past four years, nearly 50 field trials have tested similar ocean-based carbon capture strategies, from sinking rocks and crop waste to growing seaweed and fertilizing tiny ocean plants. These efforts have attracted hundreds of millions of dollars in funding, with the marine carbon credit market skyrocketing from 2,000 credits sold in 2019 to over 340,000 last year. But even that amount of captured carbon barely makes a dent in what scientists say is needed to keep the planet livable.
The approach is promising but controversial. The biggest concern? We don’t fully understand how large-scale deployment could impact marine ecosystems. “It’s like the Wild West. Everybody is on the bandwagon, everybody wants to do something,” warns Adina Paytan, an ocean scientist at the University of California, Santa Cruz. Critics argue that startups are moving too fast, with too few safeguards in place.
Like many others in the field, Planetary funds its work by selling carbon credits—certificates that allow companies to offset their own emissions by paying for carbon removal elsewhere. The concept has been around for decades, but it remains a regulatory gray area, with debates over how effective and ethical these offsets really are. Most carbon credits sell for a few hundred dollars each, but demand is growing rapidly as industries face increasing pressure to clean up their emissions.
The science behind Planetary’s approach is relatively simple: Magnesium oxide, once dissolved in seawater, helps convert carbon dioxide into stable molecules that won’t re-enter the atmosphere for thousands of years. Other startups are exploring similar techniques, using alkaline minerals like limestone or olivine.
Meanwhile, companies like Gigablue are taking a different approach, fertilizing phytoplankton—tiny marine organisms that naturally absorb carbon dioxide—off the coast of New Zealand. These efforts mimic natural processes, much like reforestation projects do on land, but with the added benefit of the ocean’s vast capacity for storage.
Will any of these strategies scale up fast enough to make a difference? Will they introduce new problems we haven’t foreseen? Will governments step in with regulations before the industry grows beyond control? These are the questions that climate scientists, policymakers, and environmental advocates are asking now.
For Will Burt, Planetary’s chief ocean scientist, the risk of inaction outweighs the unknowns. “We need to understand if it’s going to work or not. The faster we do, the better.”
