$1.75M in prepurchases made by Frontier on behalf of Stripe, Shopify, and Google to accelerate three early-stage carbon removal startups.
Pioneering ocean alkalinity enhancement and surficial mineralization, which could each remove billions of tons of CO₂ annually if scaled.
First customers secured for two out of three companies, validating breakthrough methods in carbon removal technology.
Frontier has committed $1.75 million to support early carbon removal technologies through its fifth round of prepurchases, directing funds to three startups: Karbonetiq (U.S.), Limenet (Italy), and pHathom (Canada). These deals were made on behalf of major buyers including Stripe, Shopify, and Google—marking the first-ever customer transactions for two of the three companies.
The selected projects focus on two underexplored but highly scalable pathways: ocean alkalinity enhancement (OAE) and surficial mineralization.
“These prepurchases allow us to accelerate new solutions and validate their effectiveness at scale,” Frontier stated in its announcement.
Ocean Alkalinity Enhancement (OAE)
OAE methods increase the ocean’s capacity to absorb and store CO₂ by boosting the alkalinity of surface waters. One technique, ocean liming, involves dissolving high-purity minerals like quicklime into seawater, which can remove billions of tons of CO₂ annually. Beyond carbon capture, OAE can reverse local ocean acidification, benefiting marine ecosystems such as coral reefs and shellfish.
However, the primary hurdle remains the low-emission production of quicklime, a bottleneck that one of Frontier’s new partners aims to solve.
Surficial Mineralization
This process accelerates the natural weathering reaction between CO₂ and alkaline minerals—typically found in mine tailings or industrial residues—by crushing or grinding them to expose reactive surfaces. This compresses the reaction timeframe from millennia to mere decades. Mineralization not only captures carbon but also supports mine waste remediation and critical metal recovery essential to the energy transition.
Scaling this approach hinges on minimizing energy use and emissions associated with processing, transporting, and milling feedstocks.
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Meet the Projects:
Karbonetiq
Surficial Mineralization | Santa Barbara, California | 2,142 tons
Karbonetiq uses alkaline industrial residues that naturally absorb CO₂ and cycles them through a passive aeration system enhanced by real-time sensors and software to quantify captured carbon.
“Our system improves mineralization rates and reduces land requirements,” the company explained, enabling co-location with existing industrial infrastructure.
Limenet
Ocean Alkalinity Enhancement | Lecco, Italy | 330 tons
Limenet is building a custom electric kiln to produce zero-carbon quicklime, an essential feedstock for scalable carbon removal. This clean quicklime can be used in ocean liming, surficial mineralization, and mineral looping DAC.
“We’re enabling multiple decarbonization pathways, from industrial applications to advanced CDR systems,” said Limenet.
pHathom
Ocean Alkalinity Enhancement | Nova Scotia, Canada | 510 tons
pHathom captures CO₂ from coastal bioenergy plants using a weathering reactor that combines limestone, seawater, and biocatalysts to form bicarbonate. This solution is safely released into the ocean, offering a scalable alternative to geologic CO₂ storage for coastal DAC, BECCS, and CCS.
“Our biocatalyst expands limestone’s role in carbon removal—both in oceans and on land,” the team noted.
By backing these pioneering startups, Frontier is betting on two carbon removal technologies with multi-gigaton potential—reinforcing its commitment to scale climate solutions that are scientifically sound and commercially viable.
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