Direct Ocean Capture (DOC)
Seawater conditioning and gas separation for dissolved inorganic carbon removal.
Direct Ocean Capture removes carbon from seawater. In a pH-swing route, acidification shifts bicarbonate and carbonate towards dissolved CO₂, which can then be separated as a gas. The treated water is rebalanced before return. The ocean’s subsequent exchange with the atmosphere is part of the wider carbon-removal pathway.
Working with seawater chemistry
The separation challenge is not simply to filter carbon out of seawater. Dissolved inorganic carbon exists in different chemical forms, and a change in pH alters their distribution. Intake quality, hardness, suspended solids and biological activity also influence the treatment train. Here, DOC means Direct Ocean Capture, not the water-analysis term dissolved organic carbon.
Where Lenntech technologies may fit
| Technology or task | Potential role | Design consideration |
|---|---|---|
| Filtration and UF | Reduce particles and protect downstream equipment where appropriate. | Dissolved salts and bicarbonate remain in the water. |
| ED and BPMED | Evaluate salt handling and acid/base generation in compatible process architectures. | Not every electrochemical DOC route uses bipolar membranes. |
| Degassing and membrane contactors | Evaluate transfer of dissolved CO₂ into a gas stream. | Membrane compatibility, wetting, vacuum duty and gas quality need testing. |
| NF, RO or ion exchange | Condition selected side streams or prepare utility water. | Desalinating the complete seawater feed is not an inherent DOC requirement. |
What to evaluate during development
- Salinity, pH, alkalinity and dissolved inorganic carbon
- Calcium, magnesium, suspended solids and organic fouling potential
- Acid/base balances, CO₂ recovery and energy demand
- Return-water chemistry, mixing and the project’s monitoring approach
Developing the water and separation steps
Lenntech supports water and brine treatment development through laboratory evaluation, pilot testing and engineering support. For this application, potential treatment steps can be evaluated using representative streams and clearly defined separation objectives.
The scope described here is enabling water and process support. It does not represent a proprietary Lenntech direct ocean capture process or a guaranteed carbon-removal performance.
Removing CO₂ from seawater is not itself a measurement of atmospheric removal. Air–sea exchange, downstream storage and full-process emissions must also be assessed.
Discuss your DOC project
A process outline, available water analyses and the desired separation outcomes can help frame the discussion. Contact Lenntech to explore the water-treatment scope for your concept.
Discuss water and separation requirements