School buses trundling down suburban streets this fall may smell more like french fries than exhaust fumes. That's because an increasing number of school districts are running bus fleets on biodiesel, an environmentally friendly alternative fuel often made from used cooking grease.
The switch to biodiesel isn't just good for the environment; it's also better for students. Children riding in diesel-fueled buses -- particularly buses built before tougher emissions controls were introduced in 2000 -- are exposed to significantly higher levels of harmful exhaust.
Petroleum-fueled diesel engines, which power most school buses, are notorious polluters. Regular exposure to diesel fumes has been linked with respiratory problems, cancer, and asthma -- a condition from which 6.3 million U.S. children now suffer. Children run a greater risk of developing health problems associated with air pollution than do adults, according to the Coalition for Clean Air, because their lungs are still developing.
"The ventilation systems in school buses are just not the same as those used in commercial transit buses," says Todd Campbell, policy director for the Los Angeles-based Coalition for Clean Air. Exhaust fumes get trapped inside school buses, especially on cold mornings when the windows are closed. Newer buses are designed with better ventilation features and emissions filters, but can cost upward of $100,000 per vehicle.
Several research studies conclude that air quality inside school buses is worse than outside; a Yale University study found exhaust levels inside school buses were five to ten times higher than outside them. A similar study conducted by the University of California at Los Angeles, University of California at Riverside, and the California Air Resources Board concludes that exposure to particulate matter on school buses increases a child's lifetime risk of developing cancer by 4 percent, and of developing lower-respiratory problems by 6 percent.
Though the risk of cancer and severe respiratory illness is relatively low, inhaling diesel exhaust has been linked to lesser ailments like nausea, fatigue, and memory loss -- plus missed school days.
Since April 2003, when the U.S. Environmental Protection Agency launched its Clean School Bus USA program, the agency has been working to clean up the nation's approximately 600,000 school buses, awarding $65 million in grants to schools through the plan. Clean School Bus USA gives schools much-needed funds for replacing older buses with newer, lower-emission buses and buses that run on natural gas.
But alternative-fuel advocates say the cheapest -- and most immediate -- solution to the dirty-bus problem is to switch to biodiesel, a nontoxic fuel derived from vegetable oils that requires no new equipment purchases or expensive engine modifications. More than one-hundred U.S. school districts have already switched, according to the National Biodiesel Board, and many got their funding through the EPA's grant program.
"I felt we should try biodiesel for the simple reason that it puts fewer pollutants into the air," says Edward Harkins, transportation supervisor for Mahopac Central School District in Mahopac Falls, New York. Since 2001, the district, which serves fifty-two schools in upstate New York, has been using B20, a blend of 20 percent biodiesel and 80 percent traditional diesel, in its fleet of one-hundred diesel buses. While B20 costs roughly 15 to 30 cents per gallon more than straight petroleum-based diesel, Harkins was able to squeeze the added expense into Mahopac's transportation budget without applying for special funding.
Other school districts have received anywhere from $4,550 to $21,400 from the Clean School Bus USA program to pay for the increase in fuel costs. "The natural-gas infrastructure was just too complicated and too expensive to justify," says Jerry Ryan, transportation service manager for Littleton Public Schools, of the Colorado district's decision to adopt biodiesel. Since switching its fleet of sixty-seven buses to B20 in May 2002, Littleton has even managed to save money on maintenance. "We can probably go an extra 1,000 miles between oil changes now," he says.
However, the EPA sees B20 as more of a stopgap solution than a permanent fix. Pure biodiesel, known as B100, reduces cancer-causing particulate matter by 40 percent and smog-inducing carbon by 50 to 70 percent. By contrast, B20 reduces particulate matter by only about 10 percent, and carbon by 20 percent.
Still, that's making a lot of people breathe easier.