New York City Mayor Michael Bloomberg says it's time for the city's taxi fleet to change. By the year 2012, every one of the thirteen thousand taxis in the nation's largest city will have to be a fuel-efficient hybrid. Then there are the people in Minnesota who came up with a new kind of power plant. Instead of using coal or gas, it will use tons of waste from thousands and thousands of turkeys and other birds. The nation's first poultry-litter-fired power plant begins operation next month. And it will produce enough power for fifty-thousand homes. And as any poultry farmer knows, the fuel is a renewable resource.