Surrounded by a barbed-wire fence and a green privacy screen in Broomfield, Sundrop Fuels Inc. is perhaps Colorado's "quietest" renewable energy company, writes theÂ Denver Business Journal. The company is believed to be working on a technology that could use the power of the sun to break up carbon dioxide, a pollutant, for use as a fuel in cars and trucks. Such a breakthrough would be revolutionary if commercially viable and could help solve America's energy needs and perhaps even global warming. But, frustratingly, the company isn't saying much about the project--so little that even scientists with Golden's National Renewable Energy Laboratory are left guessing. Meanwhile, the "net-zero" movement is taking hold in Colorado with houses that generate their own power using solar, wind, and underground geothermal systems. According toÂ The Denver Post, projects for thousands of such homes are under way in Aurora and in Fort Collins. Even the Legislature went green this year, pleasing the environmentally conscious among us, according toÂ The Colorado Statesman.