Cocoon Carbon Raises $15M to Turn Steel Slag Into Low-Carbon Cement, Builds U.S. Demo Plant Aiming for 10,000 Tons Per Year

Cocoon Carbon, a U.S. startup led by Eliot Brooks, has raised $15 million to build a demonstration plant that converts electric steel mill slag into a low-carbon cement substitute. The plant targets 10,000 tons of annual production, aiming to cut emissions from both steelmaking and concrete production, two of the world's most carbon-intensive industries. Steel slag is typically landfilled or used as low-value aggregate. Cocoon Carbon processes it into a material that can replace a portion of ordinary Portland cement in concrete, reducing the carbon footprint of construction. The funding round was reported by Axios, signaling growing investor interest in industrial waste-to-value climate solutions. The demo plant is located in the United States. If scaled, the process could offer a practical path to decarbonize concrete without requiring entirely new raw material supply chains, using a byproduct that is already abundant near steel mills.