As the yellow school bus again becomes a common sight on Minnesota roadways, it's also turning "green." But school buses — and privately owned vehicles transporting kids to and from school — could be even less polluting by using ever cleaner biodiesel blends.

The particulate pollution from diesel engines is particularly harmful for children, who have a faster respiration rate than adults. For kids with asthma and other conditions that compromise their lung health, exposure to diesel exhaust is an even greater health risk. Parents and school officials alike should be aware that Minnesota state law prohibits school buses from excessive idling while parked near schools.

Many of the estimated 6,000 school buses in Minnesota lack the improved diesel engines and particulate filters that are slowly being phased into school bus fleets, as new buses replace old vehicles. Some districts are retrofitting their old buses, but many simply can't afford to, especially as school budgets tighten. There is, however, a better fuel diesel buses can use.

Minnesota's new requirement
As our children board the bus and head to school this fall, the air inside and outside of the bus may be cleaner than it was a year ago, thanks to a new requirement that Minnesota's diesel fuel now contain a 5 percent blend of biodiesel. All of the school buses in Minnesota are running on this 5 percent biodiesel blend. This statewide move to B5 has the environmental equivalency of removing 55,000 cars from the road, by preventing 139 tons of particulate pollution and 330,000 tons of lifecycle greenhouse gases from entering our air each year. Even higher blends, such as B20 biodiesel, can reduce particulate pollution from school buses by as much as 11 percent.

The American Lung Association in Minnesota is encouraging school districts and school bus operators to consider using a higher blend biodiesel, where available. In 2012, all of the diesel fuel in Minnesota will be a B10 (10 percent) blend, and three years later all diesel outlets in the state will be offering B20 during the warm-weather months. In the winter, all diesel outlets will sell B5, which has been tried and tested in Minnesota winter conditions.

During a subzero cold snap last winter, some Twin Cities and national news outlets reported that biodiesel had caused a few buses to fail, leading one large school district to close. This claim turned out to be incorrect, as thousands of vehicles using the exact same biodiesel mixture operated flawlessly in even more extreme temperatures throughout the state. The problem was isolated to a single district and a few older buses of a particular design, and had nothing to do with biodiesel blended in the fuel. All biodiesel sold in the state must meet strict standards to ensure quality of the fuel.

Passenger vehicle choices
While diesel-powered passenger vehicles are still scarce in the United States, there are some on Minnesota roads right now, and more coming to the lots and showrooms. If parents are using a diesel vehicle to transport their children to and from school, biodiesel fuels are a good choice for them as well. Or, if a car or truck is one of the 200,000 or so flexible-fuel vehicles registered in Minnesota that can use E85 as well as gasoline, choosing the cleaner-burning (and cheaper) E85 will reduce emissions on the trip to and from school.

Unlike some of its neighbors, Minnesota has no fossil fuels of its own. We pipe crude oil from Canada — increasingly from the Alberta Tar Sands region — to our refineries. But we have also developed smaller biorefineries to produce our own biodiesel and ethanol fuels. These biorefineries are largely locally owned and operated, and provide an important economic boost to the state — more than $1.2 billion in net annual benefits, according to the Minnesota Department of Agriculture. Now, Minnesota has become an exporter of transportation fuels, and Minnesota drivers have more "clean air choices' at the pump than anywhere else in North America.

As a new generation of Minnesotans boards the yellow bus on the way to school, we need to do all that we can to make sure the air outside stays clean and healthy for them, and for us.

Robert Moffitt is the communications director for the American Lung Association in Minnesota.