Sun-Sentinel: Looking toward a cleaner future, this city wants to get in on the ground floor of a green energy trend: Compressed natural gas-fueled vehicles. The City Commission is expected Tuesday to give the OK to move forward with a federal grant application that would provide money to purchase vehicles — starting with trolleys — and build a natural gas service station. And one day the city could sell the natural gas for profit. To get what could be a $2.5 million grant, the city is …