British Airways, Stripe and Shopify have purchased what backers say are the first independently verified credits from ocean carbon removal, a mechanism with huge sequestration potential.
“It’s a crucial proof point that this is possible,” said Stacy Kauk, chief science officer at Isometric, the registry that issued the credits.
The credits were generated by a project that added powdered alkaline minerals to cooling water discharged from a power plant into the Halifax, Canada, harbor. The minerals trigger chemical reactions that pull carbon dioxide from the atmosphere and lock it away in bicarbonate ions, which remain stable for tens of thousands of years.
The total removed in this case was small — the three buyers will share 625 credits — but the mechanism has enormous opportunity to grow. The feedstock minerals are inexpensive and widely available in mine wastes and other sources. If scaled globally, a 2023 study concluded, ocean alkalinity enhancement conducted close to coastlines could remove gigatons of CO2. Around 10 Gt of removal will be required annually by 2050 to limit global warming to 1.5 degrees Celsius, according to the IPCC.
First movers
Stripe and Shopify are known for making catalytic investments designed to help scale early-stage removal technologies; both were founding members of Frontier, a buyers’ coalition set up for that purpose. British Airways is newer to this kind of investment. The airline made its purchase through CUR8, a London company that creates carbon removal portfolios for clients. In this case, the $12 million portfolio included future delivery of 7,000 credits from Planetary, the developer of the Halifax project.
Credits in the portfolio, which includes biochar, direct air capture and other project types, cost an average of $335 per metric ton of carbon removed, said Marta Krupinska, CUR8’s CEO and co-founder. She noted that much of the current cost of an ocean alkalinity credit comes from the procedures needed to measure, report and verify the quantity of captured carbon. Krupinska expects the total cost to fall by more than 50 percent as project developers gain experience with these processes.
Buyer confidence
If ocean alkalinity credits are to reach a market beyond first-mover companies, project developers will have to win the trust of buyers. One issue will be reliably measuring the amount of carbon removed — a challenging task in an open system such as the ocean.
For the Halifax project, Planetary took samples from the area around the discharge site and used models to estimate the captured carbon. The models included simulations of the harbor environment — calibrated using real-world measurements — and of interactions between the ocean and atmosphere.
“The ocean models used are well validated by years of measurements, and multiple simulations are run to identify what uncertainties exist across different simulations,” said Will Burt, Planetary’s chief ocean scientist. “Then, at the end, we tally all of the uncertainties across both measurements and models, and whatever that total accumulated uncertainty is, we subtract that number of credits from our total net removals. This means we are much more likely to be underestimating our removals rather than overestimating them.”
Buyers will also need to be convinced that the alkaline minerals do not damage the local environment. Isometric’s Kauk stressed that the geochemical processes involved are well understood and occur naturally. “What we’re doing is taking a natural process, then enhancing it and speeding it up,” she said. Planetary also conducted camera surveys of seabed organisms and monitored multiple metrics, including pH, to ensure that the minerals did not alter the composition of the ocean water beyond limits that had been agreed upon with scientific advisors.
Kauk said that Isometric was taking a conservative approach to help build trust and issue credits that buyers can rely on. “Then we repeat this again and again and again,” she said. “Our models are going to get better, and the market is going to start to trust marine based carbon removal as a source of very cost-effective climate benefits.
“And when those things start to be accepted by the market,” she added, “I think we’re going to hit massive scale.”
