Buses battle bitter cold
BEMIDJI — The day after Christmas break, Greg Liedl got a most-unwelcome gift: a frozen tank.
“It’s frozen,” Liedl said, showing a photo of a large chunk of DEF that was located within the tank. “The bottom quarter of this tank is frozen solid, completely.”
DEF, now required through the federal 2010 emissions standards, is quite effective at what it’s designed to do: lower exhaust emissions from diesel engines.
But it comes with a big drawback.
“It freezes at 12 degrees,” Liedl said.
An electric heater runs down into these 15-gallon tanks to keep the DEF from freezing; two lines that come into the tank from the engine also assist the heater. But when the system fails and the DEF freezes, the only thing the district can do is pull the bus inside, raise it up on lifts to drop the tank out, and then wait about 12 hours or so to allow the DEF to thaw.
“There is no way to speed it up,” Liedl said.
Buses use a selective catalytic reduction, or SCR, installed on the exhaust system of a diesel vehicle to spray DEF into the exhaust stream, thus making it burn more efficiently.
Jeff Baltzell, fleet manager for Bemidji Area Schools, said the whole system is quite effective, and he has seen it positively affect the air quality.
But the system uses five sensors, programmed to alert the engine of a potential problem. When a sensor determines something isn’t working — such as the heater — the bus goes into “D rate,” meaning it will idle but not operate.
“And there sits a $105,000 bus that you can’t use,” Liedl said.
When that happens on several buses at once, or if it occurs in combination with other vehicle problems, that can translate into a delayed school start or a missed day of class.
“The old buses, the ‘98s that I have, they started in 30, 35 below with no problem,” Baltzell said. “But I only have four of those left.”
This problem is only expected to get worse as the district purchases new buses each year, thus bringing in more and more SCR-equipped vehicles.
“As we get more of these, we’re going to have more problems,” Liedl said. “This isn’t going away.”
The district has 75 daily routes and 88 buses, of which Liedl said about 14 were purchased since the 2010 rules took effect. On Monday, the Bemidji school board authorized the purchase of four new 71-passenger buses at $91,080 each, which all meet federal guidelines, so they too will be equipped with the SRC system.
While one may wonder why the busing industry is having these problems while others, such as loggers, are not, Liedl said those workers are avoiding buying new vehicles for this reason, even investing in old engines to keep their current fleets operational.
Some area school districts, such as Wadena and Blackduck, have moved their buses indoors to get their fleets out of the elements. But those districts, like Pine River with its indoor heated garage, don’t typically have nearly as many vehicles as Bemidji.
As it is, Bemidji’s buses are outdoors and there hasn’t been much discussion of an indoor facility until this year, which admittedly has been an especially brutal winter in terms of temperatures.
“We’ve always gotten by,” Baltzell said.
When asked if other districts have found success by letting buses run overnight, Liedl said that doesn’t always solve the problem — that it only drains the batteries and doesn’t have a positive impact on whether the buses will start the next day.
In addition to dealing with existing issues, the district also is bracing for what it expects will be a whole new set of problems come summer.
“Biodiesel is going to be going to 10 percent on the first of July; she’s at 5 percent now,” Liedl said, referencing the percentage of biomaterials used in diesel. “We experienced problems not so much when it was 2 (percent) but when it went to 5.”
The district now has to annually hire someone to clean out the tanks and use additional filtering equipment to keep the tanks, and the fuel, clean.
Biodiesel can be composed with either animal fat or soy. While one product doesn’t appear to present problems, the other does.
“I’m all for soy, but the animal fat brings bacteria into the fuel and causes more troubles, contamination,” Baltzell said. “Now we’ve got to buy products to kill all of the bacteria.”
Liedl noted the fuel made with animal fat is not supposed to be made available so far north, but there aren’t set guidelines.
“Bacteria will just continue to grow and grow and grow,” Baltzell said. “That stuff is thicker than fuel or water or anything else, so it won’t go through the filter. Then, all of a sudden (the bus) won’t run because it plugs up the filter.”
Baltzell said indoor facilities would help with both the SRC system and the biodiesel, but the outdoor storage of vehicles right now is compounding the issues.
“Some of this stuff I’m an advocate for, but it just isn’t working up here in northern Minnesota in this cold weather,” Baltzell said.