The intensifying global climate crisis has prompted an urgent push for innovative solutions, one of which lies in carbon capture and storage (CCS) technologies. Among the highest emitters of carbon dioxide globally, the cement industry has long been a significant contributor to climate change. However, scientists are now harnessing this excess carbon dioxide to turn it into a sustainable solution.

A team from Northwestern University has made a groundbreaking discovery, finding a way to create carbon-negative building materials using seawater, electricity, and CO2. Their method captures CO2 and transforms it into materials like concrete and cement, while permanently storing the carbon and producing clean hydrogen gas in the process. Drawing inspiration from nature, their technique mimics how coral and mollusks form their shells. Rather than using biological energy like these organisms, the process substitutes it with electrical energy to drive chemical reactions in seawater.

The method involves using electricity to split seawater, generating hydrogen and hydroxide ions. Once CO2 is introduced into the mixture, a chemical reaction occurs, where hydroxide and bicarbonate ions combine with naturally occurring calcium and magnesium in seawater. This process leads to the formation of solid minerals such as calcium carbonate and magnesium hydroxide. These minerals effectively capture and store CO2, making the resulting material carbon-negative.

Notably, the researchers can control the texture and density of these mineral materials—ranging from flaky and porous to dense and hard—by adjusting experimental conditions. Alessandro Rotta Loria, who led the study, emphasized, “We demonstrated that when we generate these materials, we can fully control their properties, such as chemical composition, size, shape, and porosity. This flexibility allows us to develop materials suited to a variety of applications.”

What’s particularly promising is that these newly formed mineral materials can replace traditional sand and gravel in concrete production. They can also serve as raw materials for cement, plaster, and paint. Loria explains, “Cement, concrete, paint, and plasters are typically derived from calcium- and magnesium-based minerals, often sourced from aggregates like sand. Currently, sand is mined from mountains, riverbeds, coasts, and the ocean floor. But in collaboration with Cemex, we’ve found an alternative approach: instead of mining sand from the Earth, we use electricity and CO2 to grow sand-like materials in seawater.”

One of the most remarkable aspects of this innovation is the ability of these materials to store over half their weight in CO2. The amount of carbon stored depends on the mineral composition. A balanced mix of calcium carbonate and magnesium hydroxide can store more than 50% of its weight in CO2. This is significant because calcium carbonate, in nature, forms limestone—a rock that sequesters vast amounts of carbon over geological timescales. By replicating this natural process, the researchers have discovered a way to provide a long-term, sustainable method of carbon storage.

Additionally, the process produces hydrogen gas, which can be used as a clean fuel for transportation and other applications. Rotta Loria envisions a circular approach: “We could capture CO2 right at the source. If concrete and cement plants are located on shorelines, we could use nearby oceans to power dedicated reactors where CO2 is transformed through clean electricity into materials for the construction industry. These materials could ultimately become carbon sinks, contributing to our fight against climate change.”

In this way, the team’s research offers a promising blueprint for a more sustainable, carbon-neutral future in construction.

By Impact Lab