New York City-based Cella is an early-stage startup that is among a small number of firms, and the only one based in the US, trying to take CO2 mineralization from the academic realm and make it a practical solution for distributed carbon capture and storage (CCS).
The 4‑year‑old company launched its first project this year in Kenya’s Central Rift Valley and is looking to use the results to build traction within the oil and gas sector, which already has much of the equipment and subsurface expertise needed to scale the technology.
A similar research effort funded by the US Department of Energy began in 2013 and tested the injection of supercritical CO2 into volcanic basalt rocks in Washington state. Cella says its pilot makes it the second group to achieve a pure‑phase CO2 injection in reactive rock, and the first private company to demonstrate the approach for permanent mineral storage.
In geologic terms, rock formations such as basalt are known as mafic rocks. When CO2 is injected along with water, the greenhouse gas reacts over time with these rock types to form stable minerals, a process that enables permanent sequestration.
Other companies in Iceland and Oman, as well as a university research project backed by Saudi Aramco in Saudi Arabia, have pursued similar approaches, but Cella says its work differs in its ability to use significantly less water while injecting higher volumes of CO2.
The firm's recent pilot in Kenya injected 460 kg, or about 1,000 lb, of CO2 into a basalt formation using a water-alternating-gas (WAG) injection technique that is used around the world in enhanced oil recovery (EOR) projects. Cella reports a water-to-gas ratio of 10:1 in its pilot, which compares with a project in Iceland that used about 25 tons of water to dissolve 1 ton of CO2.
“What we're trying to develop as a company, is a technology that enables distributed, boutique storage solutions to solve the problem of stranded emissions,” explained Claire Nelson, the chief technology officer and cofounder of Cella.
A geologist by background, Nelson noted that Cella does not seek to compete with or replace large-scale CCS but rather complement it. The firm aims to license its technology to oil and gas producers and other companies rather than develop the projects itself. In 2024, the company partnered with Halliburton Labs, the global service company’s startup accelerator, to help its commercial efforts and raise visibility within the upstream industry.
“The CO2 storage business right now is shaping up to be a hub-and-spoke world, where you have these massive storage hubs like those in Louisiana, Texas, Indonesia, and the North Sea,” said Nelson. “But the problem that everyone needs to overcome is transportation and amalgamating enough CO2 sources to make building a pipeline worthwhile or to make the storage economics work out.”
What Cella wants to prove is that, by making it possible to create storage sites right next to an emitter, companies won’t have to spend as much on infrastructure, which often means being tied into geologic storage sites that can handle several million metric tons of CO2 per year.
While the company believes its approach can achieve such scales, it also believes it is well-positioned to make smaller-scale emission sources economic for storage projects since its approach enables them to forgo the transportation element.
A major part of this mission involves convincing emitters and oil and gas operators to consider overlooked geological sites. Nelson said a good example in the US is Iowa, where an abundance of ethanol plants sit atop mafic rock formations.
Cella’s test well in Kenya was drilled to a total depth of about 2,800 ft, which the firm sees as another potential commercial advantage since this is a much shallower depth, and thus cheaper to drill than many of the sequestration sites targeting deep saline aquifers.
Nelson explained that the process developed by Cella involves no dissolved CO2, unlike most other mineralization projects, because it borrows directly from a proven EOR process, specifically WAG.
“With WAG injections, you can tailor the water-to-gas ratio to really fit your reservoir and your project’s goals,” she said, adding that one such goal is likely to include minimizing the amount of water needed to achieve storage.
Water is not necessarily needed for mafic rock injections but it helps promote the mineralization process to take place, and pumping down more water will speed up that process. And by using the WAG method, Nelson said operators can achieve “the best of both worlds” by optimizing the cycles and timing of the injections to use less water and more CO2 while still achieving a quick mineralization process. This translates to higher levels of injection efficiency and lower overall project costs.
Of course, every rock deposit comes with its own specific properties and injection rates will also be dictated by permeability, porosity, and mineralogy.
Another advantage Cella is touting with its approach involves monitoring. Current rules in the US and elsewhere for CCS projects require that companies have plans to monitor the storage reservoirs for up to 50 years, which increases costs and complexity. Such long-term monitoring is required to ensure that the CO2 plumes and associated pressure fronts stay within the reservoir boundaries and don’t leak into formations that might impact freshwater aquifers or lead to induced seismicity.
An exception to this is if companies can prove their CO2 becomes mineralized, which means it will be stablized and won’t escape the formation. Nelson anticiaptes that this will be attractive to oil and gas companies involved in CCS because “it lowers the risk and liability, and they can walk away from a project after maybe 5 or 10 years instead of 50 years. That’s huge.”
Next steps for Cella include an additional injection test at its site in Kenya and raising new funds to drill a second well that will be used for more extensive fluid monitoring.
