Seawater, electricity and injected carbon dioxide can be used to produce calcium- and magnesium-based minerals in laboratory experiments. Those minerals could potentially serve as concrete aggregate or as inputs to other building products, but the cited study does not demonstrate a finished concrete product, commercial deployment or verified net carbon removal.
How the seawater-and-CO2 process works
A Northwestern-led study published in Advanced Sustainable Systems on March 18, 2025, investigated electrochemical precipitation in seawater while varying voltage, current density and the flow of injected CO2. The researchers examined how those settings affect mineral yield, selectivity and energy use. Read the study in Advanced Sustainable Systems.
Northwestern’s account describes electrodes applying a low electric current to seawater. The process splits water, producing hydrogen and hydroxide ions. Injected CO2 increases bicarbonate in the water; hydroxide and bicarbonate then react with dissolved ions, including calcium and magnesium, to form precipitates such as calcium carbonate and magnesium hydroxide. Northwestern’s March 19, 2025, explanation of the process describes these precipitates as materials with potential uses, rather than simply unwanted electrolysis byproducts.
What the resulting minerals might do in construction
The study supports making mineral precipitates and shows that process conditions can be varied. Northwestern reports that those conditions can tune properties such as composition, size, shape and porosity. The proposed construction role is as a possible substitute for some sand or gravel, or as an input to concrete, cement, plaster or paint—not as a demonstrated replacement for conventional concrete.
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That distinction matters on a building site: a mineral that can be produced is not automatically a qualified aggregate or a reliable ingredient in a particular concrete mix. The cited sources do not establish finished-concrete performance, durability, construction-code qualification or a product available for purchase. They describe prospective applications and a modular-reactor scale-up vision.
How to interpret the reported CO2 capacity
Northwestern says a material made of half calcium carbonate and half magnesium hydroxide can hold over half its weight in CO2; its example is that one metric ton of this composition has capacity to store over one-half metric ton of CO2. This is a capacity claim about the material’s composition, not a measured lifecycle removal rate. It does not by itself show that the full process is carbon-negative after accounting for electricity, the CO2 supply, reactor construction, transport and eventual use.
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Study lead Alessandro Rotta Loria, Northwestern associate professor of civil and environmental engineering, described the approach as one that allows researchers “to use seawater to create carbon-negative construction materials.” That is the researcher’s description of the approach; the cited work establishes laboratory research and potential applications, not commercial-scale lifecycle validation.
What must be validated before construction use
For this material to become a dependable construction input, future work would need to establish more than whether precipitation occurs. Relevant questions include:
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- Production: What mineral yield and selectivity can a process maintain, and how much electricity does it require per amount of mineral produced or CO2 retained?
- Carbon storage: How stable is the stored carbon over the relevant service life, and what are the full lifecycle emissions once energy, CO2 sourcing, reactor manufacture, transport and use are counted?
- Material performance: Can composition and physical properties be produced consistently, and how do they affect performance and durability in actual concrete formulations?
- Water and marine impacts: What treatment is needed for the seawater effluent, and what environmental effects could follow its return to the sea?
Northwestern’s account says returned seawater would require treatment and environmental verification. That is a stated condition of the scale-up concept, not evidence that marine effects have already been cleared.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Where the technology stands
The 2025 study is an early laboratory-stage route to producing potentially useful minerals from seawater and CO2. It offers a possible new source of construction material and a way to retain carbon in mineral form, but the evidence cited so far does not show a market-ready concrete, deployment at commercial scale or net-negative emissions across the full lifecycle.
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