Frontier, the carbon removal purchasing collective backed by Google, Stripe, Shopify and others, has signed a $31.3 million agreement to buy 115,211 metric tonnes of carbon removal credits from geoengineering startup Planetary.
The deal, Frontier’s first in ocean-based carbon removal, will support Planetary’s efforts to enhance ocean alkalinity — a method that could ultimately scale to remove more than a billion tonnes of carbon dioxide annually. Each tonne of carbon in the agreement is priced at $270, though Planetary aims to bring costs below $100 per tonne over time.
Unlike Frontier’s previous partnerships, which have focused on direct air capture, bioenergy with carbon capture, and enhanced weathering, this project leverages the ocean’s natural ability to absorb CO₂. Since the industrial revolution, ocean pH has fallen from 8.2 to 8.1, making seas about 30% more acidic and threatening ecosystems such as coral reefs and shellfish.
Planetary’s approach involves adding magnesium hydroxide — a compound commonly used in antacids — to wastewater treatment plants and power plants already discharging water into the sea. This increases alkalinity while minimising disruption along coastlines and lowering costs.
The company is currently running two pilot projects, one in Nova Scotia and another in Virginia. If successful at scale, its technology could play a key role in tackling both atmospheric CO₂ and ocean acidification.
