Frontier, a carbon credit purchasing consortium that counts Google and Meta as founding members, has acquired carbon removal credits from three companies.

The consortium this week announced it has facilitated $1.75 million of carbon removal purchases from Karbonetiq (United States), Limenet (Italy), and pHathom (Canada) on behalf of buyers Stripe, Shopify, and Google.

Frontier’s pre-purchase program supports early-stage companies piloting new carbon removal solutions by buying their ‘early tons’. Frontier buyers are the first customers for two out of three of the above companies.

California-based Karbonetiq takes alkaline industrial residues that naturally absorb CO2 from the air, then processes and cycles them through a low-cost, passive aeration system.

Italy’s Limenet is developing a custom electric kiln to produce zero-carbon quicklime—a clean, fast-reacting feedstock that can be mineralized and used for surficial mineralization, ocean liming, and mineral looping DAC.

Nova Scotia-based pHathom captures CO2 emissions from coastal bioenergy plants using a slurry of limestone, seawater, and biocatalysts inside a weathering reactor, forming a stable bicarbonate solution that can be safely discharged into the ocean. Frontier is buying 510 tons from pHathom.

“We're honoured to announce that Frontier has selected pHathom Technologies as a supplier in its latest carbon removal pre-purchase round,” pHathom said. “This represents catalytic validation of our approach to scalable, ocean-based carbon removal powered by verified sustainable forestry.”

“Alkalinity-based solutions could one day reach large scale,” Randy Spock, Google’s carbon credits and removal lead, said on LinkedIn. “By harnessing an existing natural process of acid-base reactions, approaches like surficial weathering (exposing rocks in the open) and ocean liming (de-acidifying bodies of water so they can more effectively regulate the atmosphere) show high potential to reach enormous scale at low cost.”

Surficial mineralization accelerates the natural reaction between atmospheric CO2 and alkaline minerals found in rocks. Ocean alkalinity enhancement (OAE) aims to increase the alkalinity of surface waters, boosting the ocean’s natural ability to absorb CO2 and store it as bicarbonate.

“One of the challenges for commercially scaling these pathways is that they can take years to achieve measurable impact on the atmosphere,” Spock added. “But in the long run the atmosphere may benefit more from that slow-and-steady approach than from faster-acting solutions with a lower ceiling for scale. Because we aim to align our portfolio with what the atmosphere needs, we’re excited to add this long-term pathway on top of our other efforts that provide more immediate help to the atmosphere, such as superpollutant destruction."

He continued: "To reach significant impact in the years to come, we need to start deploying these solutions now. Accelerating these companies’ efforts today will teach us how to optimize their approaches, and what role they might play in the broader mission of restoring the Earth’s atmosphere.”

Frontier has made at least five other deals this year. Earlier this month, the consortium signed a deal with bioenergy with carbon capture and storage firm Arbor for 116,000 tons of carbon removal credits. In March, the consortium signed a $33 million deal with enhanced rock weathering firm Eion for the removal of 78,707 tons of CO2 between 2027 and 2030. In April, the group penned a $31.6m energy-from-waste carbon removal deal with Hafslund Celsio in Norway.