Green, green grass of America's national parks

The National Parks System is protecting the environment in some farsighted ways. Turns out almost 700 pieces of equipment being used by our National Parks employ alternative fuels. The Green Energy Parks Program was started at Yellowstone in 1995 and currently is in effect at 23 parks, including Mammoth Cave. Mammoth Cave uses biofuels in all of its vehicles (everything from tour busses to lawn mowers!) and refuels on-site from two 3,000 gallon biofuel tanks. No word on where the parks get the fuel.
[Source: National Parks System]