A new Tukwila company has scored $8 million in financing to turn cow manure and trash into usable energy. Prometheus Energy Co., which has kept a low profile for the past two years, is developing a new technology that transforms the methane gas produced at landfills, cow pastures and coal mines into a substitute for diesel fuel. “What we do is take pollution and turn it into energy,” explained Daniel Clarkson, vice president of government and legal affairs at the startup. “We take waste gases … and through a freezing process turn that into liquid natural gas.”