Frontier, the carbon removal clearinghouse founded by Google, Stripe, Shopify, and others, announced today that it is buying 115,211 metric tons of carbon removal credits from geoengineering startup Planetary in a deal worth $31.3 million.
Where most Frontier deals to date have bought carbon from startups specializing in direct air capture, enhanced weathering, or bioenergy with carbon capture, the organization’s agreement with Planetary is its first to do so by enhancing ocean alkalinity.
The deal effectively prices each metric ton of carbon at $270, though Planetary says it has a plan to eventually remove carbon for less than $100 per metric ton. At full tilt, ocean alkalinity enhancement could remove over 1 billion metric tons of carbon dioxide annually.
For decades, the oceans have been dampening the effects of climate change by absorbing carbon dioxide from the atmosphere. That has slowed the pace of global warming, but it also endangers a host of marine organisms, including coral and shellfish, which depend on alkaline waters to help build and maintain their calcareous shells and skeletons.
The world’s oceans are naturally a little bit alkaline. Historically, they had a pH of 8.2, but since the industrial revolution began, it has fallen to 8.1. That might not sound like much, but pH’s logarithmic scale means the oceans are now 30% more acidic than in the early 1800s. When carbon dioxide reacts with water, it forms carbonic acid.
Planetary currently uses magnesium hydroxide to boost alkalinity, the same substance used in over-the-counter antacids. The company adds it at wastewater treatment facilities and power plants, sites that are already discharging water into the ocean. That helps minimize disruption to the coasts, and it helps Planetary keep costs down.
The startup currently has two projects, one in Nova Scotia and the other in Virginia.
Techcrunch event
San Francisco | October 27-29, 2025
Correction: Frontier revised its figures for the size of the deal after the article was published. They were originally $31.2 million and 115,208 metric tons.
