SMITHTOWN, N.Y. --- Community leaders in Smithtown, N.Y., have decided that by January all city trash-collection trucks will run on natural gas instead of diesel fuel. Smithtown is the first East Coast city to impose such a mandate. Joanna D. Underwood, an independent energy consultant, wrote in a New York Times OpEd piece that U.S. refuge truck fleets could become much cleaner and independent of foreign oil if they switched from diesel to natural gas. Trash trucks today average only 2.8 miles per gallon and burn about 8,600 gallons of diesel fuel each year, she said. There are more than 136,000 refuse trucks on American streets. About 97 percent of America's natural gas is produced in North America. From 2002 to 2005, the number of communities in the U.S. using natural gas trucks doubled -- from 26 to 57. The number of trucks expanded from 750 to nearly 1,500. California, the leader in welcoming this technology, is home to the nation's five biggest natural-gas truck fleets.