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Inside a tabletop reactor, seawater yielded pale, sand-like grains that could take the place of mined aggregate in concrete.<\/p>\n
Working with colleagues at Northwestern University<\/a>, Alessandro Rotta Loria demonstrated that the material could be grown directly from that controlled chemical setting.<\/p>\n The solids did not emerge in just one form but could appear either as loose powders in solution or as grains built onto an electrode.<\/p>\n That flexibility depends on a narrow chemical balance, which sets up the deeper question of how the material changes under different conditions.<\/p>\n How the reaction works<\/p>\n Once electricity starts moving through seawater, water splits and produces hydroxide ions, charged particles that make nearby water less acidic.<\/p>\n At the same time, bubbling carbon dioxide through the seawater creates bicarbonate ions, dissolved carbon compounds that are ready to form minerals.<\/p>\n Those ingredients meet calcium and magnesium in seawater<\/a> and solidify into calcium carbonate, the mineral found in limestone and shells, plus a magnesium-rich solid.<\/p>\n Hydrogen gas leaves the same reaction, giving the system a second product that could help pay for the process.<\/p>\n Shaping the mineral mix<\/p>\n Small changes in voltage and current, carbon dioxide flow, and water circulation produced particles that ranged from airy flakes to dense grains.<\/p>\n Under some conditions the solids clung to the electrode, while under others hydrogen bubbles knocked them loose into solution.<\/p>\n \u201cWe showed that when we generate these materials, we can fully control their properties, such as the chemical composition, size, shape, and porosity,\u201d said Rotta Loria.<\/p>\n That degree of control matters because concrete, plaster, and fillers all demand different particle sizes, densities, and open spaces.<\/p>\n Why sand matters<\/p>\n A typical concrete mix<\/a> relies on aggregates \u2013 sand and gravel that add bulk \u2013 for roughly 60 to 75 percent of its volume.<\/p>\n Replacing part of that mass with reactor-grown material could cut demand for mined sand from rivers, coasts, and seabeds.<\/p>\n Because the reactor-grown particles can form as powders or larger grains, the same chemistry could serve several building products.<\/p>\n That turns captured carbon into something that manufacturers already need in enormous quantities, which is far more useful than burial alone.<\/p>\n Some mixes become carbon negative<\/p>\n In the best mixes, the product becomes carbon-negative, storing more carbon dioxide than the process creates.<\/p>\n A blend split evenly between calcium carbonate and a magnesium-rich solid can hold more than half its own weight in carbon dioxide.<\/p>\n Later treatment with carbonation, a reaction that pulls carbon dioxide into solids, lets the magnesium-rich fraction lock away still more.<\/p>\n That extra step also changes the material itself, pushing the story from carbon storage alone toward performance inside a structure.<\/p>\n Strength after curing<\/p>\n During 30-day runs, deposits kept growing around the electrode until they formed inch-scale chunks instead of loose powder.<\/p>\n Inside the inch-scale chunks, porosity \u2013 the amount of open space in a solid \u2013 let ions keep moving and growth continue.<\/p>\n After further carbonation, compressive strength climbed from about 200 pounds per square inch (14 kilograms per square centimeter) to more than 870 (61).<\/p>\n Highly alkaline conditions still broke some aggregates apart, showing that durability will depend on where builders finally use them.<\/p>\n Keeping oceans separate<\/p>\n Instead of releasing carbon dioxide into open seawater, the team sees this chemistry happening inside modular reactors near shore.<\/p>\n Within those coastal units, operators could control incoming water, capture side products, and treat the leftover liquid before sending it back.<\/p>\n \u201cWe could create a circularity where we sequester CO2 right at the source,\u201d Rotta Loria said.<\/p>\n That matters because a promising climate tool becomes much harder to defend if it disrupts the ecosystems beside it.<\/p>\n Future research directions <\/p>\n A 2018 analysis from Chatham House<\/a> put cement production at around 8 percent of global carbon dioxide emissions.<\/p>\n For this new material to cut cement\u2019s climate burden, the electricity driving it would need to stay clean and reasonably cheap.<\/p>\n Higher voltages also triggered chlorine-related chemistry at the positive electrode, a reminder that industrial designs must manage side reactions carefully.<\/p>\n Researchers still need tougher wear tests, because construction materials fail from grinding and impact as often as compression.<\/p>\n Building ingredients that store emissions<\/p>\n Beyond concrete<\/a>, the same mineral output could feed cement, plaster, paint, or restoration projects that need calcium- and magnesium-rich solids.<\/p>\n Because the particles can grow on an electrode or fall free in solution, factories could target different supply chains.<\/p>\n That manufacturing flexibility may explain industry interest, since carbon capture survives longer when it ends as a salable ingredient.<\/p>\n What looks like waste gas in one process starts to look like raw material<\/a> in another.<\/p>\n Seawater, electricity, and captured carbon can now produce building ingredients that store emissions, replace mined material, and generate useful hydrogen.<\/p>\n Whether the idea becomes common construction practice will depend on reactor design, clean power, cost, and hard evidence from larger tests.<\/p>\n The study is published in Advanced Sustainable Systems<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read?\u00a0Subscribe to our newsletter<\/a>\u00a0for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on\u00a0EarthSnap<\/a>, a free app brought to you by\u00a0Eric Ralls<\/a>\u00a0and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Researchers have found that seawater and carbon dioxide can be turned into a solid building material that 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