Yale Environment 360: Audi is building a plant in Germany that will use surplus power produced from renewable sources, such as wind energy generated when demand is low, to produce methane from water and carbon dioxide. The plant, which will use technology developed by Stuttgart-based SolarFuel, reportedly will produce enough methane to run 1,500 of the new natural-gas vehicles Audi is planning to start selling this year. To produce the methane, the company will utilize a combination of technologies: electrolysis, in which...