SeaCURE research in Weymouth - can the ocean help us tackle climate change?

Do we need to remove Carbon Dioxide from the atmosphere?

Removing carbon dioxide (CO₂) from the atmosphere is essential for avoiding the worst impacts of climate change. This does not replace rapid and deep cuts to fossil fuel use - which remain the top priority - but complements it, helping to address sectors (such as aviation and agriculture) which are extremely difficult to decarbonise. This balance is known as Net Zero.

Why the ocean?

The ocean already holds and absorbs a large share of human-made CO₂. Because carbon is more than 100 times more concentrated in seawater than it is in air, capturing carbon from seawater, or allowing the water to hold more carbon, could be more practical than capturing carbon from air. Doing this would also not compete for space on land like many approaches would.

What is SeaCURE?

The SeaCURE project is testing a new solution that could slow down or help to reverse climate change. The process captures CO₂ from seawater and returns lower-carbon water to the ocean, helping it take in more CO₂ from the air.

The small amount of CO₂ removed in our tests is currently released back to the air, but in commercial-scale operation the CO₂ would be stored deep underground or used industrially in processes that lock it away.

For a visual explanation of the process click here, or for an explanation that goes into the chemistry click here (2.5 minute explainer video).

To prove the approach worked and to understand the real-world challenges of removing CO₂ from seawater, the team built the Weymouth pilot plant. This pilot plant is unique globally as a research facility. It is one of only three pilots of its kind in the world, and the first outside of California.

SeaCURE collaborated with SEA LIFE as they have a strong commitment to marine science and sustainability, a pumped seawater system and space for trialling technology. Together with the wealth of data available on the English Channel's biology and chemistry, these factors make Weymouth an exceptional location for testing new approaches to ocean carbon removal. We worked with Defra and the Environment Agency (EA) and all work and research is done within the EA regulations and permits.

Over a two-month trial, the team demonstrated that the SeaCURE technology works. The team also examined:

• Potential marine impacts and how to safeguard the marine environment.
• How to prove the technique actually removes CO₂ from the air.
• How much energy it might take at scale and what it might cost.
• What large-scale operation might look like, and what barriers would need to be overcome.

The project has been led and run by the University of Exeter, with the Plymouth Marine Laboratory, Brunel University of London and Eliquo Hydrok.

What about impacts on marine life?

Our pilot plant does not present a risk to marine life because the low-carbon seawater is released slowly and mixes rapidly with normal seawater. The plant uses automated controls to keep the pH of the released water below 9.5 (the upper limit for UK drinking water), which ensures compliance with our Environment Agency Permit. For more details on the permit, click here.

However, releasing low-carbon seawater into the ocean at larger scales could have unintended ecosystem impacts. Other than one recently published paper which assessed what could be said from analogous experiments, there is currently very little research available on the potential effects of low carbon water, although more research has been conducted on other ocean carbon removal approaches.

A key research priority for the SeaCURE project is to understand whether and to what extent marine impacts could occur if this or similar technologies are scaled up. To begin addressing these questions, we have carried out laboratory experiments that investigate the effects of low-carbon seawater on marine plankton (tiny plants and animals that live in the ocean) and blue mussels. Our experiments confirmed that low-carbon seawater can impact marine organisms, so it is important to dilute the decarbonised water. To find out about the laboratory experiments click here.

What's next?

Our next priorities are to:

• Understand how marine life and ecosystems would react to commercial scale carbon removal

  Some effects can't be captured in a lab, so experiments in larger on-shore tanks, and potentially at-sea floating tanks, can be used to see how different marine organisms respond over time to the released seawater.

• Demonstrate unequivocally that removing CO₂ from seawater leads to CO₂ being removed from the air.

  This could be investigated by tracking the water and simultaneously measuring and modelling how it changes.

• Broaden our research to look at enhancing the capacity of seawater to hold CO₂

  Instead of removing carbon from seawater, we can help the ocean absorb more carbon from the atmosphere by making the water slightly more alkaline. This process is commonly called Ocean Alkalinity Enhancement - to find out more click here. Here we would also investigate long-term marine impacts, challenges, and CO₂ removal efficiency.

Click here for more details about the kind of activity that could happen from SEA LIFE over the coming years.

Who is funding this?

The initial project was funded by the UK Government's Department for Energy, Security and Net Zero from 2021 to May 2025.

Since May we have been supported by the University of Exeter, and the Carbon to Sea Initiative (a non-profit that funds scientists and engineers around the world who are evaluating ocean carbon dioxide removal). Carbon to Sea have funded workshops to understand the interest and thoughts of the local community.

Local community views on the pilot will inform future funding bids, aiming to support the site as a global research hub.

Conclusion

We've shown from a two-month trial that we can remove carbon from seawater, but there is a lot more to be done. The ocean is complex and changes with tides, seasons and between years. Building a full understanding will take time and effort.

Meanwhile, we're keeping an open mind. It's too early to know which methods will work best, and we may need a mix to tackle CO₂ effectively.

The facility in Weymouth is globally unique. Continued research here helps us gather real world evidence responsibly. This evidence will help the public and policymakers decide whether ocean-based carbon removal can—and should—play a part in tackling climate change, and how we might best do this.