Scientists invent a solid carbon-negative building material

Construction is on its way to becoming greener. New research describes a method of creating building material that is not only carbon-neutral — meaning it does not produce any carbon emissions — but also carbon-negative, meaning it absorbs carbon from the atmosphere. The discovery comes at a time when reducing humans' carbon footprint is more important than ever.

A spark in the sea

Scientists have created a carbon-negative building material using just seawater and electricity, according to a study published in the journal Advanced Sustainable Systems. "Cement, concrete, paint and plasters are customarily composed of or derived from calcium and magnesium-based minerals, which are often sourced from aggregates — what we call sand," Alessandro Rotta Loria, a professor of civil and environmental engineering at Northwestern University who led the study, said in a press statement. "Currently, sand is sourced through mining from mountains, riverbeds, coasts and the ocean floor." Instead, the team found a way to "grow sand-like materials in seawater."

The researchers looked at how mollusks create their shells to devise the technique. The team put electrodes into seawater and applied an electric current. With the current on, CO2 gas was bubbled through the seawater and "changed the chemical composition of the water, increasing the concentration of bicarbonate ions," said the press statement. The hydrogen, oxygen and bicarbonate ions then reacted with the calcium and magnesium ions, which are already naturally present in sea water, and produced calcium carbonate and magnesium hydroxide minerals. Both of these products have the ability to sequester carbon.

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In addition, "the researchers were able to change the composition, size, shape and porosity of the minerals produced" by changing the conditions, including "current levels, flow rate and timing and duration of carbon dioxide injection," said Anthropocene Magazine. With this customizability, the material can be used for a number of construction purposes.

Cementing sustainability

"If the cement industry were a country, it would be the world's third or fourth-largest emitter of carbon dioxide," said the World Economic Forum. In 2022, cement manufacturing accounted for approximately 8% of the world's CO2 emissions, a significant contributor to climate change. However, building materials have the potential to be a part of the solution rather than the problem. "Replacing conventional building materials with CO2-storing alternatives in new infrastructure could store as much as 16.6 ± 2.8 billion tons of CO2 each year," said a January 2025 study published in the journal Science. "We could create a circularity where we sequester CO2 right at the source," Rotta Loria said.

The carbon-negative material could be used as a "substitute for sand and/or gravel — a crucial ingredient that accounts for 60% to 70% of this ubiquitous building material," said the press statement. "Or they could be used to manufacture cement, plaster and paint — all essential finishes in the built environment." The problem is that the "building industry can be pretty risk averse," especially without knowing the strength of the material, said Popular Mechanics. But as innovations continue, "sequestered carbon will be baked into the very fabric of the world's concrete infrastructure."