Baxter's start-up, Sustainable Energy Solutions, uses a cryogenic carbon-capture system to chill the emissions stream. When the carbon dioxide turns into an icy solid, it separates from other gases. "You get this blizzard of dry-ice flakes," he says. The CO2 is then pressurized and melted into a liquid that can be safely stored in underground aquifers. In pilot studies, the system captured 99 percent of the carbon dioxide from emissions, while costing a quarter of what conventional methods do. It also scrubs other noxious chemicals from emissions, including mercury.