How oceans can help in reducing carbon dioxide: A UK project finds the way forward

The ocean has long been recognised as one of Earth’s most vital natural allies in the fight against climate change. Acting as a vast carbon sink, it absorbs nearly a quarter of the carbon dioxide (CO₂) emissions produced by human activities, especially from the burning of fossil fuels like coal, oil, and natural gas. Now, a groundbreaking initiative on England’s south coast aims to enhance this natural process. Known as Project SeaCURE, the pilot project explores innovative technology to extract CO₂ directly from seawater, allowing it to absorb even more from the atmosphere. This approach offers a promising new tool in the global effort to reduce greenhouse gas levels.

Launched in Weymouth and funded by the UK government, SeaCURE is a small-scale pilot project exploring whether extracting carbon directly from seawater could offer a cost-effective and scalable solution to reducing atmospheric CO₂ levels. Unlike traditional carbon capture methods that target emissions at their source or draw CO₂ directly from the air, SeaCURE targets the ocean, where carbon is present in concentrations up to 150 times higher than in the atmosphere.

At the heart of the project is a simple but promising mechanism. Seawater is pumped from the English Channel into a facility where it is treated to make it more acidic. This acidification encourages the dissolved carbon in the water to transform into gas, which is then released and captured before it can escape into the air.
Professor Tom Bell from Plymouth Marine Laboratory explains it with a relatable analogy:
“When you open a fizzy drink, it froths; that’s CO₂ escaping. What we’re doing is similar: we maximise the contact between acidic water and air to release the CO₂ quickly and capture it.”
Then, the CO₂ is concentrated using sustainable materials like charred coconut husks, ready for secure storage. Once the carbon is removed, the seawater is neutralised and returned to the sea, ready to absorb more CO₂ from the atmosphere.

Currently, SeaCURE’s impact is modest. The facility removes around 100 metric tonnes of CO₂ per year, less than the emissions from a single transatlantic flight. But its developers believe the technology has enormous potential. If just 1% of the ocean’s surface water could be processed this way, SeaCURE estimates up to 14 billion tonnes of CO₂ could be removed annually, provided the system is powered entirely by renewable energy sources, such as floating solar panels at sea.

While the SeaCURE project offers hope, it also faces technical and environmental challenges. The process of generating the acidic and alkaline materials needed for carbon extraction requires significant energy. If not powered sustainably, the environmental benefits could be offset.
Additionally, concerns remain about the ecological impact of releasing large volumes of low-carbon water back into the ocean. Marine organisms such as mussels and phytoplankton rely on carbon to function, phytoplankton for photosynthesis, and mussels for building their shells. Altering the ocean’s carbon balance could affect marine life in unpredictable ways.

The SeaCURE project also sheds light on a broader issue—ocean acidification. As oceans absorb more CO₂, the water becomes less alkaline, threatening shell-forming organisms like mussels, corals, and other marine life. While the ocean remains slightly alkaline overall, even small increases in acidity can have significant ecological consequences.

Despite its early-stage status, SeaCURE is one of 15 pilot initiatives funded by the UK’s £3 million carbon capture programme. Experts believe such innovative solutions are essential to achieving net-zero emissions.
The ocean has always played a quiet yet powerful role in stabilising Earth’s climate. With projects like SeaCURE, we may be on the brink of turning that natural process into a deliberate tool for climate action. Though challenges remain, the potential is vast, and with careful research and responsible innovation, the sea may yet offer a crucial lifeline in humanity’s battle against global warming.