According to the Tacoma News Tribune, the Tacoma Public bus fleet of approximately 143 vehicles will begin fueling their large CNG buses with compressed gas produced and refined from the city solid waste facility. The article reports that the renewably produced CNG will burn in exactly the same manner as the subterranean extraction gas that has previously fueled the fleet. BEW website gives some information about the production venture. (BEW is the private corporation working with Puget Sound Energy to produce the CNG from waste.) I haven't been able to track down the energy, water and other inputs versus outputs yet, but this sounds like a promising and replicable technology that could be the difference between dirty fossil production methods and more sensible renewable ones.