A recent study published in the Royal Society Open Science in the UK suggests that a mineral called olivine can help in producing negative carbon cement. Cement production emits a significant amount of carbon dioxide, and this new process holds promise in addressing the substantial carbon footprint of cement.
A cement sample made from olivine. Image source: Helene Sandberg/Seratech
Olivine is a key component of the Earth's mantle and is found on every continent. Sam Draper from the UK company Seratech says, "It's one of the few gigatonne minerals." The company has patented a process to convert olivine into cement.
During cement production, most carbon dioxide emissions occur when heating limestone to produce clinker - a binder in cement - and when burning fossil fuels for heat. Seratech and dozens of other companies are developing low-carbon cement production methods.
Draper and colleagues are using abundant olivine reserves to replace some common clinker. Olivine contains silica, which makes cement stronger and more durable. Magnesium sulfate can also be extracted from olivine, reacting with carbon dioxide to form a mineral that can sequester gas.
Researchers dissolve powdered olivine in sulfuric acid to extract these compounds. After separating silica and magnesium sulfate, they bubble carbon dioxide through a magnesium slurry to form hydromagnesite. To scale up the process, cement plants will use captured carbon dioxide from emissions sources or the air, making the entire process carbon-negative. The remaining hydromagnesite can be recycled to make new building materials like bricks.
Researchers estimate that replacing 35% of the binder in conventional cement with silica from this process will produce carbon-neutral cement, while replacing 40% or more will yield carbon-negative cement. Draper notes that current building standards allow this material to replace up to 55% of the binder. However, researchers have not yet produced enough material for extensive testing.
For more information, refer to the research paper at: https://doi.org/10.1098/rsos.231645
