The oceans soak up almost a third of the carbon dioxide in the atmosphere. And now, researchers report that by simply applying electricity to seawater, they can convert the carbon dioxide in it to solid minerals.
Those minerals could be used “for myriad purposes in the construction sector,” says Alessandro Rotta Loria, a professor of civil and environmental engineering at Northwestern University, who led the work published in the journal Advanced Sustainable Systems. “Examples include the production of cement, concrete, plasters, and paints—materials that constitute the backbone or finishes of the built environment.”
Manufacturing cement, the main ingredient in concrete, produces 8 percent of the world’s carbon dioxide emissions. Plus, concrete requires huge amounts of sand, which is mined from coasts, riverbeds and the ocean floor. Around the world, sand mining erodes coasts, destroys habitats, pollutes groundwater, and impacts fisheries.
Researchers are always on the lookout for ways to reduce the environmental footprint of concrete. They have made cement alternatives, and proposed recycling cement or mixing waste or repurposed ingredients into concrete.
The Northwestern team has made a cement sand substitute that is carbon-negative because it traps carbon dioxide from the atmosphere and locks it away. Rotta Loria says that his team was inspired by the mechanism that marine organisms use to precipitate minerals dissolved in seawater for the formation of their skeleton and shells.
The researchers use electrolysis, the technique used to split water into hydrogen and oxygen using electricity. They basically immerse two electrodes into a tank of seawater and apply a low electrical current to split the water. Then they bubble carbon dioxide through the water, which produces bicarbonate ions.
The hydrogen, oxygen, and bicarbonate ions react with calcium and magnesium ions that are naturally present in the seawater, producing calcium carbonate and magnesium hydroxide minerals.
By tweaking the experimental conditions such as current levels, flow rate, and timing and duration of carbon dioxide injection, the researchers were able to change the composition, size, shape, and porosity of the minerals produced.
“We have simultaneously focused our attention on the opportunity to sequester carbon and synthesize useful materials with electricity that can come from renewable energy sources,” Rotta Loria says.
He adds that the process holds promise for large-scale deployment. It can be fully controlled and upscaled into modular reactors which would be especially practical when located in the vicinity of ocean and seawater. “We are currently working on optimizing all the components of the systems to demonstrate the scalability potential of this process,” he says.
Source: Nishu Devi et al. Electrodeposition of Carbon-Trapping Minerals in Seawater for Variable Electrochemical Potentials and Carbon Dioxide Injections. Advanced Sustainable Systems, 2025.
Photo by Jono Hirst on Unsplash
Image: ©Northwestern University
