Clouds of black smoke no longer fill the air when a University of Michigan transit bus pulls away from a bus stop. Instead, faint odors of french fries or popcorn waft in the air. The buses and other U-M diesel equipment now burn ultra low sulfur bio-diesel fuel which produces far fewer pollutants. And some of the buses have recently installed equipment that captures most of the particulate matter before it becomes air-borne, Pat Cunningham, director of Parking and Transportation Services, announced this week. In recent years, most diesel-fueled vehicles in the country have been burning low sulfur diesel fuel, which contains approximately 300 parts per million of sulfur. At U-M, all 110 diesel-fueled vehicles now burn 80 percent ultra low sulfur fuel, with 15 parts per million of sulfur, combined with 20 percent bio-diesel. U-M added the bio-diesel mixture, usually a soy-based product, two years ago as part of a phased environmental plan. "Our fleet-wide use of bio-diesel fuel with ultra low sulfur diesel fuel is much more environmentally friendly," Cunningham said. "We’re producing fewer pollutants while also reducing our use of fossil fuels." In addition, the 18 newest U-M transit buses are the first Gillig-manufactured buses in the country to be retro-fitted with particulate traps to capture particulate emissions. "The combination of cleaner burning fuel and the traps yields an 85-90 percent reduction in particulate matter emissions," said Dave Miller, administrative manager of Parking and Transportation Services. "The use of 20 percent biodiesel fuel further reduces all emissions by approximately 20 percent." The diesel vehicles in the U-M fleet aren’t the only ones burning cleaner. Five electric-powered trucks quietly move around campus. Also, more than 400 U-M passenger cars run on E85, which is 85 percent ethanol fuel made from agricultural products, often corn, and 15 percent unleaded gasoline. "Burning ethanol fuel reduces carbon monoxide emissions from the passenger vehicles by as much as 30 percent and carbon dioxide emissions by as much as 6 percent," said Andrew Berki, a pollution prevention specialist in Occupational Safety and Environmental Health. "Carbon monoxide is a gas that contributes to air pollution. Oxygenated gasolines, such as ethanol blends, provide a more complete combustion of the fuel, thereby lowering the levels of emitted CO." Cunningham says U-M’s fleet is the largest operation of any kind in the state of Michigan actively using alternative fuels. ‘"Our efforts also make us the foremost university in the country in use of alternative fuels," Cunningham said. "Someday, everyone else will follow our lead because it just makes good sense."