To make the most common type of cement – portland cement – limestone is extracted from quarries and burned at high temperatures, releasing large amounts of carbon dioxide. Now, a research team led by the University of Colorado Boulder has found that replacing quarried limestone with biologically grown limestone creates a net carbon neutral way to make cement, according to a statement.
Biologically grown limestone is created via a natural process that some species of calcareous microalgae complete through photosynthesis, like in coral reefs. If all cement-based construction around the world was replaced with biogenic limestone cement, the team estimate that each year around two gigatons of carbon dioxide would be saved.
“We see a world in which using concrete as we know it is a mechanism to heal the planet,” said Wil Srubar, lead principal investigator on the project and associate professor in Civil, Environmental and Architectural Engineering at CU Boulder. “We have the tools and the technology to do this today.”
The microalgae can live in warm, cold, salt and freshwaters and can therefore be cultivated almost anywhere. According to the team’s estimates, only one to two million acres of open ponds would be required to cover the U.S.’s cement requirements. The limestone is already available in limited quantities, while different companies have shown an interest in the product. Minus Materials, Inc., a CU startup founded in 2021, is bringing the research into the commercial space.
