Denver will begin using an alternative fuel in 60 city vehicles as part of a pilot project unveiled on Earth Day, April 23, according to the Rocky Mountain News newspaper. Mayor John Hickenlooper said he expects the city to use about 50,000 gallons of clean-burning B20 biodiesel by the end of the year. "This is a giant step forward in terms of the city's commitment to conservation, energy efficiency, and environmental health," Hickenlooper said. Biodiesel is produced from renewable resources, such as soybeans and mustard seed. It can be used in a pure form or blended with petroleum diesel. Denver's project will use B20 biodiesel, which is a blend of 20-percent biodiesel and 80-percent petroleum diesel. Biodiesel has been shown to emit lower levels of carbon monoxide, unburned hydrocarbons, and particulate matter than regular petroleum diesel The fuel will be evaluated for its effects on mileage, vehicle performance, and emissions. The total cost of the pilot program, which will involve vehicles assigned to the city's wastewater management division, is estimated at $15,000.