All of Minnesota's 3,200 older diesel school buses are now running cleaner, thanks to a program that performs retrofits on diesel engines.
Project Green Fleet celebrated that milestone Thursday and launched a new initiative targeting heavy construction equipment.
The program's spent about $10 million from public and private sources on retrofits to make the buses more efficient. That includes installing separate heaters so drivers can stay warm in the winter without keeping the engine idling. Another 1,400 other diesel vehicles have received new components, too.
It's the pollution equivalent of taking 750,000 cars off the road every year, said Mike Harley director of the Environmental Initiative, which runs the effort.
"We've been able to have a very big impact for air quality," Harley said. "But if we want to keep our air clean, if we want to try to remain in compliance with federal air quality standards, which is important, then we need to continue to do more."
Minnesota is currently in compliance with federal air quality standards, but there's concern the state could violate the standards in the near future.
While other states also have diesel retrofit programs, Minnesota is unique because its program is voluntary and gets ahead of any possible federal mandate to reduce pollution, Harley said.
The U.S. Environmental Protection Agency estimates that every dollar invested in diesel retrofit programs amounts to $13 in public health benefits from reducing air pollution.