PORTLAND, Maine — Breathe easy, you’re behind a Portland school bus.
That’s part of the message coming from the Portland Public Schools as the district plans to welcome its 10th bus to the fleet that uses compressed natural gas. The new bus is the latest addition in what has been an aggressive overhaul of the district’s transportation equipment over the past six years, saving the system more than 96,000 gallons of diesel fuel and nearly $173,000 over that time.
But while the shift to compressed natural gas buses has allowed the district to dodge some of the financial effect of skyrocketing gas prices in recent years, the motivation for the change was the health of the riders.
According to a Portland Public Schools announcement, the district in 2002 became aware of “several scientific studies” indicating diesel exhaust from buses is dangerous to children who ride in them — particularly students with asthma or other respiratory ailments, a group that made up about 7 percent of the system population at the time.
“We were seeing a lot of reports coming from the industry saying that diesel fumes were getting up into the buses and irritating [the riders’ symptoms],” recalled Kevin Mallory, transportation director for the district, on Monday. “With these [compressed natural gas buses], you turn them on and the only thing you see coming out of the tailpipe is water vapor.”
Portland is in a unique position in Maine to take advantage of the cleaner-running buses, because the city’s Metro bus system has a compressed natural gas filling station for the vehicles, providing convenient access that Mallory said no other district in the state has.
By the start of school on Sept. 6, the compressed natural gas buses will make up nearly half the fleet — 10 of the district’s 24 buses. With just a few exceptions, Mallory said the remainder of the diesel buses in the fleet run with additives or engine modifications to help clean up the unhealthy emissions that at one time were considered common for buses.
The district also adopted a no idling policy for its buses.
“We can now say that 40 percent of the fleet is extremely clean, and the rest of the fleet — with the exception of a few vehicles left over from the 1990s that we keep in reserve — are very clean high efficiency diesel,” he said.
Mallory said the compressed natural gas buses cost more to purchase up front than diesel buses — with price tags of about $125,000-$130,000 each instead of the diesel vehicles’ costs of $90,000 apiece — but save money at the pump. He said compressed natural gas buses can be filled up for the equivalent of $1.21 per gallon, while the average diesel cost over the past year was $3.10 per gallon.
“That’s a lot of money, and we’re putting it all back into the classroom,” Mallory said of the fuel savings.
He also said Portland Public Schools has been able to take advantage of federal grant money, administered locally through the Maine Department of Environmental Protection, to cover about half the cost of each compressed natural gas bus the district has bought.
Mallory said he plans to request three more buses in the upcoming school budget cycle, with grant money availability to determine whether those new buses will be running on compressed natural gas or modified diesel.
“I hope we can replace them all with compressed natural gas buses at some point,” he said.
“When I started [in Portland in 1996], it didn’t matter; you just belched it all out,” Mallory continued. “Kids should be very happy now with the products we’re putting out for them to ride to school. They’re clean and efficient.”