Carbon-Negative Building Material Made From Seawater and CO2
The material can hold up to half its weight in trapped CO2 and replace sand in concrete.
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Researchers have successfully developed a new carbon-negative material using seawater, electricity and carbon dioxide (CO2).
The material – a mineral precipitate formed during a modified seawater splitting process – can store half its weight in trapped CO2 and can be used as a replacement for sand in the production of concrete, or in certain plasters and paints.
The research, published in the journal Advanced Sustainable Systems, also found that altering the applied voltage, current and CO2 injection rate during the precipitation process can tailor the properties of such minerals.
From trash to treasure
Seawater splitting is a process commonly used in green hydrogen production. Using a cathode and anode powered by a source of renewable electricity, the seawater is electrolyzed and splits to produce hydrogen gas at the cathode and oxygen or chlorine gas at the cathode.
During this electrochemical process, mineral deposits of calcium carbonate (CaCO3) and magnesium hydroxide (Mg(OH)2) also slowly build up at the cathode – especially when there is a high amount of dissolved CO2 present in the water. These deposits have generally been dismissed as an energy-intensive byproduct by those who produce green hydrogen. However, some believe that these minerals could have untapped potential for carbon sequestration.
“Traditionally, mineral precipitates similar to those analyzed in this work are considered an unwanted byproduct of green hydrogen production. This is because they typically increase the electrical resistance of the process, leading to higher energy consumption,” lead study author Dr. Alessandro F. Rotta Loria, told Technology Networks.
“As a part of our work, we have devised controllable ways to synthesize these minerals and engineer their deposition onto cathodic interfaces or directly in solution,” he explained. “This capability enables us to tailor the properties of the precipitated minerals to suit desired engineering applications.”
Storing carbon with sea minerals
To produce their materials, the researchers inserted electrodes into a large reactor filled with seawater and applied an electric current while bubbling CO2 gas through the water. Molluscs form their shells by a similar process, using their metabolic energy to convert dissolved ions into calcium carbonate; the researchers use electrical energy as a replacement and increased the mineralization with the injection of extra CO2.
This extra CO2 becomes effectively “trapped” as it interacts with the ions present in seawater – the formation of CaCO3 acts directly as a carbon sink, while the Mg(OH)2 produced can also sequester some carbon through additional interactions.
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By varying different experimental factors – including the applied voltage and current, the flow rate and duration of CO2 injection and the recirculation of seawater in the reactor – the researchers were also able to vary the composition and properties of the carbon-sinking minerals produced. Depending on these factors, the minerals can be made to be more flaky and porous or denser and harder.
“These factors collectively influence the precipitation process in a highly complex manner, as it strongly depends on local pH, ionic availability and type, temperature and other variables,” Rotta Loria explained. “Through our work, we have developed an understanding of how to simultaneously control all these variables to achieve mineral precipitations with desired properties while also optimizing the energy input required to obtain the intended outcomes.”
Depending on these factors and the resultant ratio of minerals produced, the deposited material can trap approximately half its weight in CO2.
Towards more sustainable construction
The researchers believe that this material, in addition to simply acting as a carbon sink, could also be used as a component in construction materials without compromising on their strength.
“The precipitated minerals can be utilized in the production of various cements, such as magnesium-based cements, as well as plasters and paints,” Rotta Loria said. “Additionally, these minerals can be cultivated as large-scale aggregates for use in concrete manufacturing.”
Producing enough cement to meet demand while also reducing emissions in line with a “Net Zero by 2050” target has already been identified as a particular challenge by the International Energy Agency, with current emissions figures remaining stubbornly high despite the required 4% annual reduction needed to meet that goal. Using carbon-negative materials in the production of cement and concrete could help to improve the footprint of this industry.
To be useful in such an application, it is critical that the production method for such carbon-negative materials is highly scalable. This is something that this new method delivers, Rotta Loria believes.
“The developed process utilizes highly modular components that can be integrated into scalable reactors for large-scale deployment, featuring real-time monitoring and product quality control. As a result, this approach holds significant scalability potential. The project team is actively progressing in this direction,” Rotta Loria said.
“On the scientific side, several questions remain regarding the mineralization process, the answers to which could further enhance its control. On the engineering side, multiple steps are required to industrialize the technology,” Rotta Loria said. “However, the knowledge we have developed uniquely positions us to effectively tackle these challenges.”
Reference: Devi N, Gong X, Shoji D, et al. Electrodeposition of carbon‐trapping minerals in seawater for variable electrochemical potentials and carbon dioxide injections. Adv Sustain Syst. 2025:2400943. doi: 10.1002/adsu.202400943
About the interviewee:
Dr. Alessandro Rotta Loria is the Louis Berger Junior Professor at Northwestern University, where he directs SOIL (the Subsurface Opportunities and Innovations Laboratory). He is also the co-founder of the startups GEOEG and ENERDRAPE.
Alessandro’s work lies at the intersection of mechanics, energy and electrochemistry. His overarching objective is to develop a fundamental understanding of the impacts of energy transfers on the structure-property relationship of geological and granular materials. This work aims to address pressing challenges and opportunities for cities and territories, ranging from sustainable construction and infrastructure preservation to subsurface urban heat islands, sea-level change and geological energy harvesting and storage. Through these efforts, Alessandro strives to decarbonize the construction sector, innovate infrastructure, foster the renewable energy transition and conserve the natural and built environments.
Dr. Alessandro F. Rotta Loria.
Credit: Michele Marie.
