Six of the nation's 10 largest sources of carbon dioxide emissions are coal-fired power plants in the South, but year after year Southern lawmakers balk at pushing utilities toward cleaner renewable energy. Last month, Republican senators from the South provided about half the votes that defeated federal legislation to require power companies to get 15 percent of their electricity from renewable sources by 2020. Nationally, almost half the states have adopted their own renewable mandates, but only one, Texas, is in the South. Southern lawmakers -- responding to heavy lobbying from local utilities -- argue their region isn't conducive to solar or wind power like the sun-baked Southwest or the open plains of the West.