Minerals can be used to create carbon-negative cement by capturing CO2

An abundant mineral called olivine helps make carbon-negative cement. This process could help tackle cement's large carbon footprint. Cement accounts for about 8 percent of the world's CO2 emissions.

Olivine is one of the main components of the Earth's mantle, and reserves are found on every continent. “This is one of the few minerals available on a gigaton scale,” he says. sam draper UK-based Seratech has patented a process to turn olivine into cement.

Dozens of startups like Ceratec are developing low-carbon ways to produce cement, including replenishing steel byproducts and recycling the carbon dioxide released in cement production. Most emissions occur when limestone is heated to produce clinker, the binding agent in cement, and fossil fuels are burned to generate heat.

Draper and his colleagues turned to the more abundant olivine to find an alternative to some of the usual clinkers. Olivine contains silica, which makes cement stronger and more durable. Magnesium sulfate can also be extracted from it, and this salt reacts with CO2 to form a mineral that sequesters the gas.

The researchers extracted these compounds by dissolving powdered olivine in sulfuric acid. After separating the silica and magnesium sulfate, they bubbled CO2 into the magnesium slurry to form a mineral called nesquehonite. To scale up the process, Draper said cement plants would use CO2 captured from sources or the atmosphere, making the entire process carbon negative. The remaining nesquehonite could potentially be recycled into new building materials such as bricks.

The researchers estimate that replacing 35 percent of regular cement in a concrete mix with silica from this process produces a carbon-neutral cement, while subbing more than 40 percent makes it carbon negative. Draper said current building codes allow this type of material to replace up to 55 percent of cement, but it has not yet been manufactured in sufficient quantities to conduct robust testing. There is.

This process uses a well-known reaction. Rafael Santos Located at the University of Guelph in Canada, it offers a novel and “rational” way to combine them. But some of the chemicals they contain are difficult to recycle, he says.