Ocean Alkalinity Enhancement

Ocean Alkalinity Enhancement (OAE) —

Topics: OAE Grants Startups

OAE moving from the lab to the ocean with new research guidelines, government funding, and business startups

July 8, 2025 | geoCDR News

Ocean alkalinity enhancement (OAE) is the least developed of the geologic methods of carbon dioxide removal (CDR), having been tested only in computer models and small-scale experiments in the lab and ocean.

Other geologic methods of CDR such as ERW and DACPS have either been implemented at large scale or are on the verge of doing so. But OAE remains in only the experimental stage, having not yet been tested at a large scale in the ocean.

Big questions remain about how much CO₂ OAE can remove from the atmosphere and how spreading large amounts of rock dust in the ocean will impact marine life.

Progress is being made toward answering those big questions, however. Recently, technical guidelines were published for how to effectively conduct research on OAE. And, new government funding in the U.S. for developing verifying carbon removal methods will add further incentive to OAE development. Also, new businesses are being created that are testing the waters of OAE by proposing pilot projects at several locations in the ocean.

These new developments in OAE are located mainly in Europe, North America, and Australia, with little attention paid to OAE in Africa and Asia as found . . . Read more

Topics: OAE

OAE developer, Planetary Technologies, scaling out as well as up

June 18, 2025 | Tom Kaldenbach, geoCDR News

Planetary Technologies has been on a roll since 2022 when it first obtained funding for testing its ocean alkalinity enhancement (OAE) strategy. The process involves adding magnesium hydroxide (Mg(OH)₂) to coastal ocean water to make the ocean more alkaline (less acidic), thus enabling the ocean to absorb more CO₂ from the atmosphere. The company is . . . Read more

Topics: OAE

Italian OAE developer, Limenet, joins Carbon Business Council and forges ahead with new plant and working capital

June 12, 2025 | Tom Kaldenbach, geoCDR News

Limenet, an Italian climate tech start-up focused on ocean alkalinity enhancement (OAE), recently announced in a LinkedIn post that it has become a member of the Carbon Business Council — a nonprofit trade association uniting companies working to restore the climate.

This membership is the latest milestone in Limenet’s push to establish itself as a leader in ocean-based carbon removal using its patented process. In September 2024, the company launched its first modular carbon dioxide removal facility in Augusta, Sicily, a major step toward scaling up ocean carbon storage. The plant converts atmospheric CO₂ into stable calcium bicarbonate (Ca(HCO₃)₂) dissolved in seawater and is designed to process up to 100 kilograms of CO₂ per hour.

Adding to its credentials, Limenet recently secured ISO 14064-2 certification from RINA, an international standards body, for its carbon removal methodology. This recognition places the company among a small group of firms globally whose processes meet rigorous verification standards . . . . Read more

OAE Basics

The OAE process is similar to the ERW process in that both processes involve crushing or to a powder (to make it more soluble), and then spreading the rock powder on the ocean surface (OAE) or a land area (ERW). OAE aims to buffer (lower the acidity) of ocean water which would accelerate the naturally-occurring process of atmospheric CO₂ (in rain water) dissolving in ocean water on the ocean surface.

Chemical reactions in ocean water - Like ERW, OAE is essentially a series of acid-base reactions. Simplistically speaking, carbonic acid (H₂CO₃) in rainwater dissolves rock powder, resulting in a chemically neutral solution in ocean water composed of bicarbonate (HCO₃^-), a base, charge-balanced by calcium (Ca²⁺) and magnesium (Mg²⁺) which are acidic.

Deployment status - OAE currently is only in the testing stage. There have been no large-scale commercial OAE projects. A small number of research trials are being performed at a few locations by researchers in the public and private sectors.

Environmental impacts - Potential adverse impacts from OAE include impacts to marine life from trace metals (e.g., nickel and chromium) in rock powder and chemical components generated in the OAE reactions (e.g., bicarbonate, calcium, manganese, and iron). Clouding ocean water with rock dust could also adversely impact marine life.

Carbon negative status - OAE requires a significant amount of energy to mine, grind, and transport rock powder feedstock. Low- or zero-carbon energy sources will be necessary for an OAE project to be carbon negative (i.e., remove more carbon dioxide than the project produces). A cradle-to-grave assessment of a project is necessary for verifying the project will be carbon negative.

Cost per ton of CO₂ removed - The cost of OAE is poorly defined due to OAE's untested status. Costs will include: mining, grinding, transporting, spreading rock powder, and . The potential range of cost per ton of CO₂ removed has been to use >60 of electricity. Assuming electricity use is 80 kWh, and electricity costs $0.20 (USD) per kWh, grinding cost for 1 ton of basalt would be $16.

Measurement, reporting, and verification () - Accurate verification of carbon removal amounts will be necessary if the OAE industry will be funded by the sale of carbon credits. Verification include sensors which directly measure alkalinity of the water (more bicarbonate equals more alkalinity) and water samples (which can be analyzed for bicarbonate and alkalinity in a laboratory). Computer modelling is also an important part of verification.

Side benefits of OAE - Making ocean water more alkaline via OAE may help the adverse effects that ocean acidification is predicted to have on calcifying marine life (e.g., corals, molluscs, plankton).

CO₂ storage durability - CO₂ converted to bicarbonate (HCO₃^-) and stored in ocean water is considered to be virtually permanent .

Long-term global CDR potential - Future implementation of OAE as a CDR method is unknown. The ocean may be able to store of tons of CO₂ with limited changes in bulk chemistry. This compares to the 1,000 (1 trillion tons) of CO₂ needing removal from the atmosphere within the next century according to the .

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