Colorado-based Prometheus Materials has developed masonry blocks from a low-carbon, cement-like material grown in micro-algae bioreactors that reproduce like coral. "Coral reefs, shells, and even the limestone we use to produce cement today show us that nature has already figured out how to bind minerals together in a strong, clever, and efficient way," says co-founder Wil V Srubar III. It eliminates most, if not all, of the carbon emissions associated with traditional concrete-based building materials like Portland cement. Biomineralizing cyanobacteria are grown using sunlight, seawater, and carbon dioxide, and then mixed with aggregate. Colorado professors developed the material in response to a US Department of Defense call to envision sustainable materials. Prometheus Materials, founded in 2021, plans to create a precast material for roofing tiles, wall panels, sound barriers, and other concrete elements in the next two years.