Frontier facilitates second round of carbon removal purchases

December 15, 2022

In its largest round to date, Frontier has facilitated $11M of carbon removal purchases—from Arbor, Captura, Arca (formerly Carbin Minerals), Carbon To Stone, Cella, CREW and Inplanet—on behalf of Stripe and Shopify. In addition, Stripe has provided $500K in R&D grants to Kodama Systems and Nitricity.

This purchase cycle Frontier received more than twice as many applications as it did during its first cycle, six months ago. Applications spanned more than 10 different carbon removal pathways.

Along with prepurchases like those announced today, Frontier is actively reviewing candidates for offtakes—larger multi-year agreements with companies ready to start scaling their technologies. Read more about Frontier’s purchasing tracks here.

Carbon dioxide removal (CDR) is critical to achieving climate goals, alongside radical emissions reductions. Models project that by 2050 we will need to permanently remove billions of tons of CO₂ from the atmosphere every year.

Observations from this purchase cycle

  • Increasing diversity in approach | We’ve added a wider range of new carbon removal solutions—from direct ocean capture to direct air capture coupled with alkaline material mineralization, biomass burial, and integrating carbon storage into clean fertilizer production. Several of these are taking on research and technical gaps Frontier highlighted in its database, including exploring enhanced weathering in tropical soils and advancing the development of CO₂ mineralization in underground basalt formations.
  • New permanent storage sinks | CO₂ capture is often coupled with geologic storage. But, in many parts of the world, storing carbon underground is costly or not a readily available option. New approaches that do away with the need for geologic storage are emerging. These include combining direct air capture with alkaline materials (e.g., steel slag) to produce carbonates that can be used in building materials and containerized rock weathering that can use impure CO₂ streams as an input.
  • Using industrial waste streams | The waste streams of existing industrial processes are fertile ground for exploring carbon removal opportunities. Many companies are attempting to use mine tailings, steel slag, flue gas from organic waste incineration, biomass waste from forest thinning for wildfire management, or brine from desalination plants. These approaches have the benefit of providing a low-cost feedstock for carbon removal, leveraging existing infrastructure and waste heat, and in some cases, actively cleaning up and reducing the impacts of waste that would otherwise have to be disposed of.
  • Optimizing the use of waste biomass | We evaluated a number of compelling proposals this round for CDR using waste biomass, and think that the best solution(s) co-optimize between waste stream accessibility, carbon removal efficiency, permanence, and cost, as well as secondary benefits like avoided emissions. We purchased from one approach that is rethinking biomass gasification and turbine design, which reduce capital costs while increasing CO₂ removal. In addition, Stripe awarded a research and development grant to explore the effectiveness of burying biomass from forest thinning operations, a potential pathway for maximizing carbon removal efficiency.

The projects

Stripe and Shopify will spend a combined $3.5M buying carbon removal, with another $7.5M contingent on projects reaching agreed upon technical milestones. Stripe will spend a further $500K supporting R&D from Kodama Systems and Nitricity. To view project applications, purchase contracts, and renewal criteria, visit Frontier’s GitHub.


Biomass Carbon Removal and Storage | Los Angeles, US | 1,000 tons

Biomass Carbon Removal and Storage (BiCRS) is a process that removes CO₂ from the air through biomass and stores it. Arbor is developing a scalable and low-cost approach to BiCRS based on modern rocket engine technology. The team brings together deep experience in turbomachinery, combustion, and manufacturing. Their modular systems combine compact gasification with a supercritical CO₂ turbine, offering feedstock flexibility, high electrical efficiency, and permanent geologic storage.


Surface Mineralization | Canada and Australia | 380 tons

Mine waste, or "mine tailings," has the potential to trap CO₂ when exposed to air and water. Arca is accelerating this process by using autonomous rovers to stir the tailings and increase the speed of CO₂ weathering reactions with the alkaline material. This approach eliminates the costs usually associated with moving tailings to a processing site by enabling the reaction to happen on-site. The team is also developing a pre-treatment technology to further increase the CO₂ reaction rates and reduce costs.


Direct Ocean Capture | Pasadena, US | 508 tons

Oceans store a quarter of the CO₂ emissions generated by human activity. Captura is developing a sea-based electrodialysis machine that generates a sequesterable stream of atmospheric CO₂ directly from ocean water. Captura’s direct ocean capture approach has the potential to reduce removal costs by eliminating the need for air contactors and sorbent/solvent and utilizing existing infrastructure such as desalination plants and oil and gas platforms.

Carbon To Stone

Enhanced Weathering | Ithaca, US | 1,269 tons

Carbon To Stone is developing a new approach that couples Direct Air Capture (DAC) with mineralization. Conventional DAC processes use heat or pressure changes to regenerate solvents reacting with CO₂, resulting in high energy use. Carbon To Stone chemically regenerates the solvent by reacting it with alkaline material such as steel slag, fly ash, or mine tailings to produce carbonates that could be used for alternative cements. This approach reduces both the energy and the cost required for the same tonnage of CO₂ captured.


In-situ Mineralization | US and Kenya | 2,198 tons

Cella is accelerating the process of converting CO₂ into a mineral by injecting it into volcanic rock formations together with saline water and geothermal brine waste. Typical in-situ mineralization approaches are water intensive, but Cella’s design recycles 100% of the injected water. Their approach has the added benefits of integrating low-carbon geothermal heat, which reduces the cost of DAC, and disposing of geothermal brine which is usually a waste product.


In-situ Mineralization | New Haven, US | 615 tons

CREW is developing a container-based solution to enhanced weathering, making it quicker and cheaper to deploy. In this first project, they will co-locate with a wastewater treatment facility to remove carbon resulting from the incineration of organic waste, but the system can flexibly capture CO₂ from a variety of sources. The system consists of weathering reactors that increase the speed of reaction of CO₂, water, and carbonate or silicate feedstock. CREW’s ability to measure and quantify system effluent will serve as a model that researchers can use to better understand weathering reactions and ensure that the discharge doesn’t affect local ocean ecosystems. Ultimately, storage of CO₂ as bicarbonate ions in the ocean is a secure and scalable storage method.


Enhanced Weathering | Germany and Brazil | 1,041 tons

Inplanet uses enhanced weathering (EW) to permanently sequester CO₂ and regenerate tropical soils. While most EW studies to date have been conducted in Europe and North America, Inplanet will be deploying this technology in Brazil, where warmer and wetter conditions could result in faster rock weathering rates and thus faster CO₂ drawdown. Inplanet will be teaming with local mines and quarries to source rocks, and with the University of São Paulo to develop monitoring, reporting, and verification (MRV) field stations to collect better data on how weathering changes with different silicate rocks under a variety of weather and soil conditions across Brazil.

Kodama Systems

Biomass Burial | Sonora, US | R&D Grant

Kodama Systems, in partnership with the Yale Carbon Containment Lab, is running a pilot in the Nevada desert to bury woody biomass thinned from forests at risk of wildfires. Biomass burial has the potential to be a low cost and highly efficient form of CDR (defined by how much carbon in the biomass gets stored), but there are open research questions regarding durability, such as the rate of decomposition. Kodama is using a novel approach to construct underground “vaults” that minimize water, oxygen, and microbial activity that could decompose the biomass, while employing numerous surface sensors to detect any decomposition. By determining optimal vault designs, they will be able to minimize CDR costs and maximize storage durability.


Other | Fremont, US | R&D Grant

Nitricity is integrating carbon removal into an innovative process for the production of clean fertilizer. Traditionally, the production of nitrophosphates for the agricultural industry is an energy- and emission-intensive process. The Nitricity team is pioneering a carbon-free process to make nitric acid, and is testing the use of atmospheric CO₂ for a subsequent carbonation reaction that yields nitrophosphates while permanently storing the carbon in the form of limestone.

Be part of our next purchases

Frontier is an advance market commitment to buy an initial $925M of carbon removal between 2022 and 2030.

If you are a carbon removal supplier building an early-pilot, precommercial facility, or an at-scale deployment, we’d love to hear from you. You can find more details about Frontier’s purchase process here.

If you are interested in becoming a buyer of carbon removal through Frontier, please get in touch at