KAIST turns dissolved ocean carbon into permanent mineral storage

New electrode design solves mineral-scaling problem

Device runs 120 consecutive hours on Jeju lava seawater

From left: Ko Dong-yeon, professor at KAIST's Department of Biological and Chemical Engineering; T. Alan Hatton, professor at MIT's Department of Chemical Engineering; Park In-hwan, KAIST doctoral candidate; and Lee Young-hoon, MIT doctoral researcher. [KAIST]

South Korean researchers have developed a technology that converts carbon dissolved in seawater into a stable mineral form for effectively permanent storage — and solved a long-standing hardware problem that had hampered the approach's commercial viability.

KAIST announced Tuesday that a research team led by Ko Dong-yeon, a professor in the Department of Biological and Chemical Engineering, had jointly developed "electrochemical dissolved inorganic carbon ocean carbon removal" (e-DOC) technology with a team led by T. Alan Hatton, a professor at the Massachusetts Institute of Technology.

The ocean absorbs roughly 30 percent of the carbon dioxide humans emit, making it the planet's largest carbon sink. Just as water refills a bucket after some is scooped out, removing dissolved CO2 from seawater prompts the ocean to draw down more from the atmosphere — a dynamic that has made ocean-based carbon removal a focus of climate research.

The research team developed a method to convert dissolved inorganic carbon (DIC) in seawater into calcium carbonate, a mineral form that does not re-enter the atmosphere. Carbon stored this way remains sequestered effectively permanently, allowing the ocean to continuously absorb fresh CO2.

Existing technologies, however, suffered from a "scaling" problem in which minerals such as calcium carbonate accumulated on electrode surfaces — much like limescale building up inside a kettle. Performance degraded over time, requiring frequent cleaning or replacement and driving up energy consumption and maintenance costs.

To overcome this, the team developed a hollow-fiber electrode assembly (HFEA) — a concentric structure built inside a hollow, thread-like electrode that integrates an ion-selective membrane with a counter-electrode to trigger the electrochemical reaction.

In short, the team redesigned the device so that minerals form on the outside of the electrode rather than on its surface, preventing the scaling that had plagued earlier systems.

In this configuration, most minerals precipitate outside the electrode rather than on it. Hydrogen bubbles that naturally form at the electrode act like a brush, continuously sweeping the surface clean and keeping mineral deposits from adhering.

In experiments using lava seawater from Jeju, the device ran stably for more than 120 consecutive hours, removing 80 to 90 percent of dissolved inorganic carbon from the seawater while cutting energy consumption by up to 54 percent compared with existing technologies.

The process also yielded high-purity hydrogen and magnesium hydroxide as byproducts. Magnesium hydroxide is used as an eco-friendly material and industrial feedstock, and the team said the dual production of these byproducts improves the technology's economic viability.

The device can be built in a compact, modular form, making it suitable for installation on ships and offshore platforms. The team said it hopes to scale the system up into a large-scale ocean carbon removal platform that can contribute to carbon neutrality and climate action.

"This technology converts CO2 dissolved in seawater into a mineral form that does not return to the atmosphere, storing it permanently and helping the ocean continuously absorb new CO2," Ko said. "We expect it will accelerate the commercialization of ocean carbon removal technology and contribute to realizing a carbon-neutral society."

Park In-hwan, a doctoral candidate in KAIST's Department of Biological and Chemical Engineering, and Lee Young-hoon, a KAIST alumnus now at MIT's Department of Chemical Engineering, served as co-first authors. The findings were published online in the journal Advanced Energy Materials on June 19.

woo@heraldcorp.com