Carbon buying consortium Frontier has signed a $31 million carbon removal agreement with Planetary, an ocean alkalinity enhancement (OAE) firm, for the removal of 115,211 tons of CO2 between 2026 and 2030.

Frontier, which counts Meta and Google as founding members, will support Planetary in the expansion of its pilot project that, in June, delivered the world’s first verified OAE credits. The Tufts Cove OAE project, in Nova Scotia, Canada, was successful in generating 625.6 carbon credits.

“This offtake with Frontier buyers allows us to demonstrate that ocean alkalinity enhancement can safely and effectively remove CO₂ beyond small-scale trials. This approach could be the cheapest and most scalable carbon removal solution. We're eager to show how it can be rolled out responsibly,” said Mike Kelland, CEO, Planetary.

According to Planetary, its approach has the potential to become one of the most effective means of carbon removal, with a credible path to under $100 per ton.

Planetary’s approach works by adding dissolved alkaline minerals, such as calcium oxide or magnesium oxide, to coastal waters. This enhances the ocean’s natural capacity to capture carbon by converting dissolved CO2 into bicarbonate ions, which are stored in the ocean for more than 10,000 years.

The process uses existing coastal infrastructure, like power plant cooling water outfalls, allowing deployment without major new construction. According to Planetary, unlike biological methods, OAE relies on the ocean’s chemical buffering system, minimizing impacts on marine ecosystems and food webs.

“Ocean alkalinity enhancement can remove CO2 from the atmosphere extremely cheaply and efficiently. But expanding it beyond small-scale trials calls for ironclad measurement and safety protocols, alongside addressing community concerns. Planetary is taking on these challenges head-on with a rigorous MRV approach and thoughtful community engagement at their Tufts Cove site. This is the right project and team to pave the way forward for this promising pathway,” said Hannah Bebbington, head of deployment, Frontier

Planetary has said it will make all project findings publicly available.

Frontier has backed several other alkaline mineral addition solutions. These include deals with land-based enhanced rock weathering firms such as Terradot, Lithos, and Eion, and freshwater-focused companies including CarbonRun and CREW.

The consortium has also signed numerous other carbon offtake deals. For example, in July, it signed a deal with bioenergy with carbon capture and storage firm Arbor for 116,000 tons of carbon removal credits.