SeaCURE: Seawater Carbon Unlocking and Removal


What is SeaCURE?

The SeaCURE project is developing technology that removes carbon dioxide (CO2) from seawater. The natural concentration of carbon in seawater is much higher than in air – so capturing CO2 from seawater promises to be more scalable and affordable than Direct Air Capture techniques.

SeaCURE makes use of natural processes. The sea is a major reservoir of dissolved carbon and SeaCURE removes this as CO2 before releasing low-carbon seawater back to the sea where it naturally absorbs more carbon from the atmosphere to replace the CO2 that was removed. The removed carbon can be stored permanently in rock formations using established technology.

Powered by renewable energy, SeaCURE has the potential to remove vast quantities of CO2 from the atmosphere to help avoid or recover from dangerous climate change.

Why do we need to capture carbon?

Rising levels of CO2 in the atmosphere are causing global warming. To avoid the worst impacts of climate change, humanity must dramatically reduce emissions of CO2 and other greenhouse gases. SeaCURE is not an alternative to this – emissions must be reduced as fast as possible – but residual and historical emissions also need to be mitigated if we are to maintain a pathway to a safe climate.

What goes in? What comes out?

The SeaCURE plant takes in ordinary seawater, then removes about 90% of the dissolved carbon from that water. In continuous operation no chemicals are added or removed other than CO2, so the only substance released back into the sea is carbon-depleted seawater.

Low carbon seawater is less acidic than ordinary seawater. This water is rapidly diluted with the surrounding seawater and absorbs CO2 from the atmosphere. After CO2 absorption from the atmosphere is complete, the released water is chemically identical to the surrounding seawater.

What would happen to the removed carbon?

CO2 taken from seawater can be stored geologically – beneath the ground in wells previously emptied of oil and gas, or crystallised into the natural pores within rocks. Geological storage of CO2 has been happening for over a decade and is known to be effective and safe. The carbon could also be used by other industries instead of fossil fuel-derived CO2.

At the scale of this pilot project, the amount of carbon we remove unfortunately does not justify geological storage. Instead we are engaging with partners who can make use of the CO2.

Where will the pilot plant be built?

The pilot plant will be built in Weymouth within an existing building. Seawater will be drawn onto the site and released through existing infrastructure. The plant will operate for short periods from 2024. We plan to dismantle the plant at the end of 2024, with no trace left behind.

Where will future SeaCURE plants be built?

If the pilot is successful, our analysis suggests that future plants would be most effective if built offshore, decarbonising seawater at large scales in the open ocean and thereby helping to ensure a safe climate for all life on Earth.

Is there any risk to wildlife or people using the waters near the technology?

The CO2-depleted seawater that will be released is within the pH (acidity) range allowed for UK tap water, and has a CO2 concentration between that of tap water and seawater. We will be monitoring the water at all stages of the process to make sure it meets the regulations set by the Environment Agency.

Who is funding this work?

The work is completely funded by the UK Government’s Department for Energy, Security and Net Zero. The project will not be funded through the sale of carbon or carbon removal credits.

Published 31/01/2024