Brimstone

Ordinary portland cement (OPC), the binder in most forms of concrete, is made by heating limestone (calcium carbonate), a process that releasese huge amounts of CO2 — about 8 percent of the world’s annual total. To meet climate goals without crippling the global construc­tion industry, nations need a zero-carbon or carbon-negative ways to make cement. Brimstone makes OPC by feeding calcium-silicate rocks such as basalt, rather than limestone, into its kilns. The process produces calcium oxide — the key ingredient in cement — without releasing carbon, and if Brimstone’s kilns are heated with renewable energy, the overall process is carbon-negative.