The production of cement is responsible for about 8 percent of all GHG emissions resulting from human activity globally. To make cement, which is the binding element for concrete, limestone is mined, crushed, and baked by burning fossil fuels. In addition, almost two-thirds of cement’s emissions are due to the release of carbon dioxide otherwise locked in the limestone. Sustainable cement and concrete is a growing research topic for Stanford. One Stanford team is prototyping cement that instead uses volcanic rock that contains all the necessary building blocks, but none of the carbon.