Frontier, a carbon-buying consortium backed by Meta and Google, has signed two pre-purchase agreements totaling $3.05 million with early-stage carbon removal firms.

The deals with French firm Pronoe and US company Cella are intended to support both companies in moving from pilot-stage deployments to commercial scaling by funding equipment buildout and data-collection efforts, before it can secure long-term offtake agreements with the companies.

French firm Pronoe is a developer of modular water-treatment units designed to connect to desalination plants and other coastal facilities. The company’s systems work by dissolving crushed limestone into seawater using an electrically driven process, producing an alkaline discharge that increases ocean alkalinity and enhances the ocean’s ability to absorb CO2.

The company claims that, unlike other ocean alkalinity enhancement (OAE) approaches, its system avoids lime calcination and on-site CO2 storage, which reduces emissions and infrastructure requirements. Frontier said that this design could allow for faster scaling by leveraging existing coastal infrastructure. The agreement is Frontiers’ first with a French carbon removal company.

The deal is Frontiers’ second with an OAE firm in the last 12 months, following a $31m agreement with Planetary to remove 115,211 tons of CO2 between 2026 and 2030 last August.

Cella is a US company pioneering a carbon removal process called carbon mineralization. The process works by accelerating mineralization in deep basalt formations, where injected CO2 reacts with rock to form stable mineral carbonates. Frontier claims that the approach offers high permanence, low water use, and flexibility to pair with multiple CO2 capture technologies.

The pre-purchase is expected to fund a second injection well to expand CO2 handling capacity at a direct air capture demonstration hub in Kenya, while generating operational data to reduce technical and regulatory risk for the pathway.

The deal is the second between Frontier and Cella, with the carbon buying consortium inking a pre-purchase deal with the company back in 2023.

Frontier signed several carbon removal deals in 2025, including a $44.2m deal with Canadian biowaste carbon-capture and storage firm Nulife GreenTech for 122,000 tons of CO2 between 2026 and 2030, in December.

The month before, it signed a deal with biogas carbon capture firm Reverion to remove 96,000 tons of CO2 between 2027 and 2030. As part of the deal, Frontier buyers will pay Reverion $41m.

In March, the consortium signed a $33m deal with enhanced rock weathering firm Eion for the removal of 78,707 tons of CO2 between 2027 and 2030.