Cement scientist Brent Constantz wants concrete to be the "hero" that cleans up dirty coal. "The reality is, coal is not going away," he says. "We need to meet the world’s power demands without emitting more carbon." His answer? A new type of concrete that sequesters carbon without disturbing its traditional binder: portland cement.

This past summer, the Stanford University professor’s Los Gatos, Calif.-based startup, Calera Corp., began making cement from flue gas and seawater at Dynegy’s gas-fired 1,500-MW Moss Landing Energy Facility. At first, Constantz hoped to replace portland cement, which emits about one ton of carbon dioxide per ton produced. But after some industry pushback and more research, he now says he can use Calera aggregate synthetic stone, sand and gravel to capture CO2 and still produce net gains.