Holding half its weight in carbon dioxide, the material could replace sand in concrete and other construction materials while trapping greenhouse gas.
Holding half its weight in carbon dioxide, the material could replace sand in concrete and other construction materials while trapping greenhouse gas.
The construction industry may soon build with materials that actively remove carbon dioxide from the atmosphere, thanks to an innovative process developed by Northwestern University researchers who have essentially found a way to grow sand from seawater and CO2.
The research team, led by civil engineer Alessandro Rotta Loria, has created a carbon-negative material that could replace conventional sand in concrete while permanently storing greenhouse gases. Their findings, published Wednesday in Advanced Sustainable Systems, demonstrate a process that not only traps carbon but also produces hydrogen as a clean fuel byproduct.
“We have developed a new approach that allows us to use seawater to create carbon-negative construction materials,” said Rotta Loria, the Louis Berger Assistant Professor of Civil and Environmental Engineering at Northwestern’s McCormick School of Engineering. “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.”
The technique represents a significant shift from current practices. “Currently, sand is sourced through mining from mountains, riverbeds, coasts and the ocean floor,” Rotta Loria explained. “In collaboration with Cemex, we have devised an alternative approach to source sand — not by digging into the Earth but by harnessing electricity and CO2 to grow sand-like materials in seawater.”
From Seawater to Building Materials
The process starts surprisingly simply: researchers insert electrodes into seawater and apply an electric current. This splits water molecules into hydrogen gas and hydroxide ions. While keeping the current flowing, they bubble CO2 gas through the seawater, changing its chemical composition and increasing bicarbonate ion concentration.
These chemical changes trigger reactions with naturally occurring calcium and magnesium ions in seawater, producing solid minerals like calcium carbonate and magnesium hydroxide – similar to the materials in seashells and coral.
“Our research group tries to harness electricity to innovate construction and industrial processes,” Rotta Loria said. “We also like to use seawater because it’s a naturally abundant resource. It’s not scarce like fresh water.”
The researchers discovered they could not only grow these minerals into sand-like materials but also precisely control their properties. By adjusting factors like voltage, current, CO2 injection rate, and seawater flow, they could create substances ranging from flaky and porous to dense and hard.
“We showed that when we generate these materials, we can fully control their properties, such as the chemical composition, size, shape and porosity,” noted Rotta Loria. “That gives us some flexibility to develop materials suited to different applications.”
A Double Climate Solution
The carbon-trapping capacity of these materials is remarkable – they can store more than half their weight in CO2. For instance, one metric ton of the material (composed half of calcium carbonate and half magnesium hydroxide) could permanently sequester over half a metric ton of carbon dioxide.
This development comes at a critical time for the construction industry, which faces growing pressure to reduce its substantial carbon footprint. According to the World Economic Forum, the cement industry alone accounts for approximately 8% of global CO2 emissions, making it the world’s fourth-largest carbon emitter. When combined with concrete production, this environmental impact grows even larger.
The Northwestern study, co-authored by Jeffrey Lopez, an assistant professor of chemical and biological engineering, along with postdoctoral fellow Nishu Devi and several PhD students, represents part of a broader collaboration with Cemex, a global building materials company focused on sustainable construction.
Rotta Loria emphasizes that the material’s integration into concrete or cement wouldn’t compromise structural integrity. “This approach would enable full control of the chemistry of the water sources and water effluent, which would be reinjected into open seawater only after adequate treatment and environmental verifications,” he said.
From Lab to Industry
The researchers envision scaling up their technique using modular reactors rather than implementing it directly in the ocean, which could disturb marine ecosystems. The approach could be particularly effective at cement and concrete plants located near shorelines, creating a circular system where carbon dioxide emissions are captured and transformed into useful construction materials.
“We could create a circularity where we sequester CO2 right at the source,” explained Rotta Loria. “And, if the concrete and cement plants are located on shorelines, we could use the ocean right next to them to feed dedicated reactors where CO2 is transformed through clean electricity into materials that can be used for myriad applications in the construction industry. Then, those materials would truly become carbon sinks.”
The nature-inspired process mirrors how marine organisms like coral and mollusks form their shells – using energy to convert dissolved ions into calcium carbonate. But instead of metabolic energy, the researchers apply electrical energy and enhance mineralization by injecting CO2.
While many climate solutions focus on capturing carbon dioxide and storing it underground, Northwestern’s approach adds value by turning greenhouse gases into usable materials for manufacturing concrete, cement, plaster, and paint – all while generating hydrogen as a clean fuel with various applications, including transportation.
As the construction industry searches for ways to reduce its climate impact, this technique suggests a future where building materials could help address the climate crisis rather than contribute to it – transforming what we build with from an environmental liability into an environmental asset.
Categories Earth, Energy & Environment, Technology Tags carbon sequestration, Climate Change Solutions, Green technology, Innovative Building Materials, sustainable construction
Did this article help you?
If you found this piece useful, please consider supporting our work with a small, one-time or monthly donation. Your contribution enables us to continue bringing you accurate, thought-provoking science and medical news that you can trust. Independent reporting takes time, effort, and resources, and your support makes it possible for us to keep exploring the stories that matter to you. Together, we can ensure that important discoveries and developments reach the people who need them most.