Researchers from the Massachusetts Institute of Technology (MIT) said they have discovered the key to removing carbon dioxide directly from ocean water, which absorbs 30-40% of carbon emissions prevailing in the atmosphere.

The inexpensive method can mitigate Co2 emissions and could potentially lead to overall net negative emissions. The findings were reported in the journal Energy and Environmental Science.

The team came up with a reversible process consisting of membrane-free electrochemical cells. Reactive electrodes were used to release protons to the seawater, driving the release of the dissolved carbon dioxide from the water.

The team said the process is cyclic wherein it first acidifies the water to convert dissolved inorganic bicarbonates to molecular carbon dioxide, which is collected as a gas under vacuum.

Following this, the water is fed to a second set of cells with a reversed voltage, to recover the protons and turn the acidic water back to alkaline before releasing it back into the sea.

Periodically, the roles of the two cells are reversed once one set of electrodes is depleted of protons (during acidification) and the other has been regenerated during alkalization.

The researchers said this removal of carbon dioxide and the reinjection of alkaline water could slowly start to reverse, at least locally, the acidification of the oceans that have been caused by carbon dioxide build-up.

Once the carbon dioxide is removed from the water, it will still need to be disposed of, as with other carbon removal processes.

For instance, it can be buried in deep geologic formations under the sea floor, or it can be chemically converted into a compound like ethanol, which can be used as a transportation fuel, or into other specialty chemicals.

The team said initially the idea would be to couple such systems with existing or planned infrastructure that already processes seawater, such as desalination plants.

Thus carbon dioxide removal could then be a simple add-on to existing processes.

For instance, the system could also be implemented by ships that would process water as they travel, to help mitigate the significant contribution of ship traffic to overall emissions.

There are already international mandates to lower shipping’s emissions, and could help shipping companies offset some of their emissions, and turn ships into ocean scrubbers,” the researchers said.

The system could also be implemented at locations such as offshore drilling platforms, or at aquaculture farms. Eventually, it could lead to the deployment of free-standing carbon removal projects distributed globally.

The process could be more efficient than air-capture systems because the concentration of carbon dioxide in seawater is more than 100 times greater than it is in air, the team asserted.

Currently, the research is continuing and the team expects that the system could be ready for a practical demonstration project within about two years.

Recently, European Union member states and parliamentarians have agreed on a major reform to the bloc’s carbon market or emission trading system to reduce emissions and encourage investments in climate-friendly technologies.

In November 2022, government think-tank NITI Aayog’s study found that carbon capture utilization and storage are key to ensuring sustainable development and growth in India, particularly for producing clean energy.

Image: MIT