In a laboratory in Daejeon, South Korea, scientists have figured out how to turn dissolved carbon dioxide from the ocean into something like stone — permanently locking it away so it can never return to the atmosphere. The research team, led by Professor Dong-Yeun Koh from KAIST along with Professor T. Alan Hatton at MIT, developed an electrochemical system that removes carbon dioxide from seawater and converts it into calcium carbonate, a mineral found in chalk, marble, and seashells.
The ocean is Earth's biggest carbon storage, absorbing about 30 percent of all the carbon dioxide humans release into the air. When we take carbon dioxide out of seawater, the ocean naturally pulls more from the atmosphere to refill it — like water flowing back into a glass someone just emptied. The team's technology converts that dissolved carbon into a mineral form that cannot escape back into the air, letting the ocean keep absorbing more.
A key problem with older technologies was mineral buildup. Just as limescale gathers inside a kettle, calcium carbonate would stick to electrodes and clog the system over time, reducing efficiency and requiring costly repairs. The team solved this by designing hollow fiber electrode assemblies — tiny thread-like fibers bundled together. Minerals form on the outside of these fibers instead of directly on the electrode surface. Even better, tiny hydrogen bubbles produced during the process act like a brush, continuously cleaning the fibers and preventing scale from building up.
In experiments using seawater from Jeju Island, the device ran continuously for more than 120 hours while removing 80 to 90 percent of dissolved carbon from the water. It also used 54 percent less electricity than existing technologies. As a bonus, the process simultaneously produces clean hydrogen gas and magnesium hydroxide, a material used in flame retardants and other industrial products, making the technology more economically attractive.
Professor Koh said the system could be built in a compact, modular form and installed on ships, offshore platforms, and other marine facilities. The team is now working to scale up the technology into large marine carbon removal systems that could help fight climate change. "This technology enables permanent storage and helps the ocean continuously absorb new carbon dioxide," Koh said. "We expect this work to accelerate the commercialization of marine carbon removal technologies."