Demonstration of direct ocean carbon capture using encapsulated solvents

Direct ocean carbon capture (DOC) is an emerging form of negative emissions technology that requires expedited characterization and comparison against more well-established forms of carbon capture. Using microencapsulated solvents for DOC affords large membrane surface areas for carbon dioxide (CO2) in the ocean water to flux across a gas-permeable membrane, and reversible regeneration of the contained solution. The feasibility of using a packed bed of Na2CO3 capsules to extract CO2 from seawater is assessed here through lab-scale experimentation, one-dimensional modeling, and techno-economic assessment (TEA). The experimental flux measurements match the flux predictions of the 1D model, validating the model. Parametric studies with our capsule bed model suggest that for a balance between pressure drop and breakthrough time the optimal capsule diameter is between 400-600μm, the optimal bed porosity is between 0.5-0.7, and the optimal seawater velocity through the bed is 0.10-0.15 m/s. The TEA estimates that the carbon capture cost of a 1 MTonne/year greenfield system using Na2CO3 capsules would be exorbitant: $8,977.14 per tonne of CO2. This work demonstrates the potential of using microencapsulated solvents for direct ocean carbon capture and illustrates a need for further research to reduce system costs. [Display omitted] •Sodium carbonate microcapsules are capable of removing carbon dioxide from seawater.•CO2 removal rates can be improved with smaller capsules and higher temperatures.•Technology is not currently cost-competitive due to high capital costs of microcapsules.