TRAVERSE CITY -- Biodiesel no longer is used in Traverse City school buses, but its remnants live on -- as about eight inches of sludge coating the bottom of a fuel tank.
The cost to clean the tank could be an additional general fund expense, said Phil Haldaman, transportation director for Traverse City Area Public Schools.
Biodiesel can congeal in colder temperatures and has been gathering for years, Haldaman said.
"If you can imagine molasses in January, that's the consistency," he said. "It's almost like tar."
The fuel contains 5 percent "green" components and 95 percent diesel, and was phased out of service at the start of this school year. Higher costs and new devices aimed at reducing emissions led to the switch, Haldaman said.
About 15 percent of the district's fleet had used biodiesel since its introduction about five years ago.
Cleaning the tank coincides with a planned overhaul this summer of the district's fuel island. The work will repair cracking concrete, realign the pumping stations and attempt to prevent contamination.
Budgeted for $400,000, Haldaman estimated construction could finish closer to $325,000, to be paid for with bond revenue.
The fuel island has four pumping stations with two hoses each, as well as four 10,000-gallon underground tanks. One of them contained the alternative fuel.
As of Tuesday, biodiesel cost $1.45 a gallon, about 8 cents more than ultra-low diesel. But it previously has cost up to an extra dime.
TCAPS purchases about 350,000 gallons of fuel each year.
"We try to save money and we try to do the right thing with greening initiatives, but it always comes with a price tag," Haldaman said. "We didn't want to take away bio without doing something else."
A $150,000 grant from the Environmental Protection Agency allowed administrators to install a device similar to a catalytic converter on all 125 buses about two years ago, reducing hydrocarbon emissions by 50 percent and carbon monoxide by 40 percent, according to the EPA.
Both are cleaner fuels, but biodiesel on its own is better at reducing emissions, said Sheila Batka, an environmental scientist with the EPA regional office in Chicago.
Emissions are even lower from both when using the new technology, she said.
Ideally, schools would use 100 percent biodiesel, said William Koucky, who this summer intends to open Northwest Michigan Biodiesel, a small-scale plant that would turn canola and used cooking oil into the fuel.
But when budgets get tight, he said, extras like biodiesel often are cut.
"It's tough," Koucky said. "I don't approve, but what are you going to do?"
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