Dozens of YMCA summer campers filed out of a yellow school bus outside the Minnesota Science Museum in St. Paul, preparing for a day of learning about the environment.
The students didn't realize their school bus was a science project in itself, part of a nine-year effort to reduce school bus pollution.
On Thursday, the Environmental Initiative celebrated the completion of Project Green Fleet, which provided fuel-efficient engines for more than 4,600 diesel vehicles across the state, including 3,200 school buses used by about 200,000 students.
The result was the equivalent of removing 750,000 cars from the road.
"We're one of the first states to say that, and to do it in a voluntary way," said Mike Harley, executive director of the Minneapolis-based nonprofit.
The Environmental Initiative's partnership with the Minnesota Pollution Control Agency has provided cleaner engines for every eligible school bus in the state (some buses were too old for retrofitting, while newer ones did not require it). The state contributed $2.4 million to the effort, and a recent $1 million grant from founding sponsor Flint Hills Resources meant the project came at almost no financial cost for each school district.
Thursday's celebration didn't mark the end of Project Green Fleet. Next up: reducing diesel emissions for at least 100 construction vehicles in the state.
The process, which requires actually removing and replacing old engines, costs $60,000 to $80,000 for each construction vehicle. Project Green Fleet hopes to pay for about half the cost of the retrofitting, and the rest would be paid by construction companies. An industry spokesman said that participating in the project requires industry players to invest a great deal of time and money.