Ocean Carbon Sequestration: Scaling Marine Climate Solutions Fast

Takeaways

• Oceans already absorb a quarter of global CO₂ emissions, and scientists believe they could remove far more through new marine carbon dioxide removal (mCDR) approaches.
• Solutions range from engineered technologies to nature-based systems like mangroves and seagrass, but scaling, verification, and permanence remain major challenges.
• Strong private investment and emerging policy frameworks are accelerating innovation in blue carbon solutions, despite uncertainty around cost and long-term impact.

The world’s oceans have long acted as a natural buffer against climate change, absorbing about a quarter of all carbon dioxide emissions produced by human activity, roughly 2.4 billion tonnes each year. But scientists and climate technology firms are now asking a bigger question: Can the seas safely store even more carbon and help slow global warming at scale?

Early estimates suggest the potential is significant. Emerging marine carbon dioxide removal (mCDR) approaches could, in theory, remove an additional 8 billion tonnes of CO₂ annually by 2050. According to Shaun Fitzgerald of the Centre for Climate Repair at the University of Cambridge, the ocean represents “one of the biggest opportunities to take carbon dioxide out of the atmosphere.”

However, experts caution that ocean-based climate solutions must avoid the mistakes seen in some land-based carbon projects, where environmental gains were sometimes reversed or not truly additional. This has made the marine research community highly cautious, says Sophie Chu of Captura, a California Institute of Technology spinout working on electrochemical carbon removal from seawater.

Read More: Blue Carbon: Japan to Store CO₂ in Deep Sea with Marine Plants

Two Pathways: Engineered and Nature-Based Solutions

Ocean carbon removal strategies broadly fall into two categories. Engineered solutions, such as Captura’s system, use technology to extract CO₂ directly from seawater. Nature-based approaches rely on ecosystems such as mangroves, seaweed, and seagrass to capture and store carbon naturally.

Mangroves, in particular, are drawing strong interest. Studies suggest they can store up to 1,000 tonnes of carbon per hectare, while also protecting coastal communities from storm surges and supporting fisheries. Yet questions around permanence remain; storms, development, or ecosystem damage could release stored carbon back into the atmosphere.

To address these risks, coalitions such as Symbiosis, which includes companies like Google, Meta, and Salesforce, are backing blue carbon solutions while emphasizing rigorous verification and long-term monitoring.

Engineered Capture Gains Momentum

On the engineered side, companies like Captura and Planetary Technologies are advancing ocean alkalinity enhancement (OAE) and direct seawater carbon extraction. Captura’s system, for example, uses renewable electricity to split water into streams that enable CO₂ removal and storage, while returning treated water to the ocean.

These technologies are being supported by major advanced market commitments, including Frontier Climate, whose backers include Stripe, Shopify, and Google. Such funding is helping scale pilot projects into early commercial operations.

Still, measurement remains a critical challenge. Scientists emphasize the importance of ensuring that “a tonne is a tonne” when it comes to carbon accounting. Advanced monitoring, reporting, and verification (MRV) systems are being developed to address uncertainties in ocean carbon fluxes.

Policy and Investment Shaping the Future

Momentum is also building at the policy level. Europe is working on carbon removal certification frameworks, while Japan is exploring compliance markets that include coastal blue carbon. These developments are expected to strengthen confidence in ocean carbon sequestration projects.

Also Read: China Launches First Oil Production Ship with CO₂ Capture

Despite technological progress, experts acknowledge a trade-off: Higher certainty in carbon removal often comes with higher costs and lower scalability. Yet supporters argue that the cost of inaction may be far greater.

As Fitzgerald notes, ignoring the ocean’s potential would mean overlooking one of the planet’s most powerful natural climate systems, one that may prove essential in the race to stabilize the global climate.

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Source: Reuters