A 2010 Funding Odyssey

Emissions from new school buses are getting cleaner, but at what cost?

By Bill Siuru

Diana Mikelski is concerned, and for good reason.

The supervisor of transportation for Wauconda CUSD 118 located in the northwest Chicago suburbs has seen firsthand school bus purchase costs rise due to the EPA’s 2007 engine emission requirements. Meanwhile, school budgets are shrinking amid even stricter engine regulations in 2010.

“We keep getting less money from our state, but we have to absorb $7,000-plus increases in buses for just emissions. I guess we buy less or keep the old and hope for the best,” says Mikelski. “Someone will give us the money to install products, but the maintenance, training and long-term effect of those products as well as the engine modifications is not considered.”

EPA regulations are driving cleaner medium- and heavy-duty diesel technology in the U.S., calling for 0.01 g/bhp-hr PM (particulate matter), 0.2 g/bhp-hr NOx (nitrogen oxides) and 0.14 g/bhp-hr NMHC (non-methane hydrocarbons) emissions by 2010. The PM standard is already in full effect and is being meet by the 2007 model-year engines already hitting the streets. The NOx and NMHC requirements are being phased in with complete compliance by 2010.

“With the new technologies across the line, with ABS and other sensors all over the place, the (maintenance) guys are going goofy trying to keep up,” Mikelski adds. “We have five different computers regulating different things.”

The Wauconda technicians have been receiving training on the intricacies of the district’s 10 new 2008 model-year buses with diesel particulate filters. But one bus had to be taken out of commission for extra maintenance work performed at the dealer. Mikelski said her biggest concerns are repairs and increased costs associated with the 2010 mandate. Wauconda runs Blue Bird transit-style Visions that utilize Cummins diesel engines, which will use Selective Catalyst Reduction (SCR) technology.

While cleaner diesel engines are great news for the environment and community health, just how can school districts pay for added purchase costs for newer, seemingly more labor-intensive buses? Unfortunately, there are no easy answers, as IC Bus’ Keith Kladder points out.

“The federal government provides billions of dollars in subsidies for mass transit each year,” he says. “Currently, the federal government does not recognize school bus transportation as mass transit.”

There are local grant programs, like one utilized by Wauconda to pay for retrofitting 29 older buses with diesel oxidation catalysts. The EPA provided some funding for clean diesel and alternative fuel projects via its Clean School Bus USA program. But with the program now combined with the $6 billion Congestion Mitigation and Air Quality (CMAQ) Improvement Program, it is neither clear how funding for 2010 school buses will compete with the heavy-duty trucking and mass transit industries nor how school buses will meet the various and complicated requirements for funds set forth by the Federal Highway Administration and the Federal Transit Administration. Numerous efforts, such as that of the revamped American School Bus Council, are currently underway to rectify the omission of school buses from mass transit and to lobby for CMAQ funding,

What it all Means
While added costs to meet 2007 requirements averaged around $7,000, the incremental cost to meet 2010 has yet to be pinned down. In June, the National Truck Equipment Association suggested that new emission control technology may add as much as $8,000 to a diesel-powered truck. School bus cost increases will likely be in the same ballpark.

The big question may be the cost difference between SCR and enhanced Exhaust Gas Recirculation (EGR) and improved fuel management, which may offer one supplier an advantage over another. Engine makers say this added, up-front cost can be recovered by fuel savings, since the new engines are expected to be more fuel efficient. For instance, Navistar says its 2007 MaxxForce medium-duty engines are showing seven- to 12-percent fuel economy improvements.

The 2010 engines could also require another type of fluid to be carried aboard buses, meaning added maintenance costs and possible headaches. There are two accepted ways to meet the 2010 requirement to reduce NOx emissions. Cooled EGR is essentially an extension of technologies used to meet the 2007 requirements. SCR requires the use of another fluid, urea or aqueous ammonia. With SCR reduction, a small amount of urea is injected into the exhaust stream upstream of the SCR catalyst. The ammonia generated from the urea within the SCR catalyst converts the NOx into benign nitrogen and water vapor.

IC Bus says MaxxForce will meet the 2010 emissions standards without urea. The Warrenville, Ill., manufacturer and Caterpillar announced a global alliance in June that included a plan to cooperate on development of the MaxxForce for school buses that supports “each company’s stated path not to utilize urea-based Selective Catalyst Reduction.” Meanwhile, Cummins has been marketing its MidRange engines using SCR in Europe, and it announced last year it will do the same in 2010 for school buses, though its heavy-duty engines will use EGR. Detroit Diesel looks to be headed in the same direction.

IC representatives say the 2010 MaxxForce engine will use advanced fuel systems, air management, combustion and controls to preclude the need to use SCR for NOx after-treatment. Technologies that could be used include partial HCCI (Homogeneous Charge Compression Ignition), higher injection pressures, improvements on turbocharger boost and variable valve actuation. Although this will add to the cost of a new school bus, IC says it will not be as much as the more complex SCR approach that requires additional vehicle hardware, sensors, electronic calibrations and the use of urea injection SCR.

Proponents of SCR point out it is already in widespread use in more than 500,000 heavy-duty SCR-equipped trucks in Europe as well as hundreds of thousands of diesel-powered cars. AUS32, Aqueous Urea Solution 32.5-percent, is marketed in Europe by the trade name AdBlue. Currently, there are more than 1,600 AdBlue retail pumps across Europe, and the number is growing.

Using urea will probably not add to the fuel bill, but questions remain on the labor costs of filling up and maintaining the more complex SCR system. Typically, the mixture is a blend of 5-percent urea to 95-percent diesel. In a school bus that gets 6 mpg, this equates to about 8 gallons of urea per 1,000 miles. In Europe, the cost per liter of urea is about half that of diesel, equivalent to about $4 per U.S. gallon, mainly because it is not as heavily taxed.

Breaking Down Urea
Urea promises fuel economy increases, albeit by small amounts, because SCR allows engines to be tuned and calibrated to improve efficiency. Because the catalytic reaction occurs after combustion, diesel fuel is also not needed to burn NOx. The Daimler-Benz experience in Europe shows trucks with SCR are showing fuel economy improvements between 3- and 5 percent.

A major concern is the need for a new infrastructure to distribute this new fluid, and there’s already anxiety in over-the-road truck operators. Urea is expected to be available in 2.5-gallon jugs at larger truck stops around the country by next year. Separate urea storage tanks probably will not be required but might allow bulk purchase to reduce its cost.

Adding to its availability is that fact that automakers, including Mercedes-Benz, BMW, Audi, Volkswagen, Mini, Hyundai, Kia and Jeep, will be marketing diesel vehicles meeting the 2010 standards so they can be sold in all 50 states. The approach most are taking is to carry enough urea on-board so refilling can be done at normal service intervals.

What about other concerns with urea? The first organic compound to be artificially synthesized from inorganic starting materials, it is not harmful to the environment and poses no real hazard if used properly. It is used as a fertilizer as well as in food products, chewing gum, skin cream and pharmaceuticals. When the urea solution is injected into the hot exhaust gas, some ammonia is created that exists for a fraction of a second before it is decomposed into harmless nitrogen and water in the SGR catalyst. If a trace amount happens to escape, it is captured by the last element in oxidation catalysts specifically designed to decompose it completely.

At over 105 degrees Fahrenheit, urea will decompose rapidly, and it will freeze at about 10 F. Experts say this should not pose a problem, as school bus fleets operating in colder climates rarely store other fluids like windshield washer fluid or even oil outside. Urea also thaws very quickly from the warmth radiated by the engine tank and supply system. Users need to know that urea tanks must be well-insulated to prevent decomposing in hot climates and heated in cold weather. AdBlue is now routinely used in Europe from the Mediterranean to the Artic Circle.

But questions remain if buses will be able to run without urea, such as during the first few minutes of warm-up, a practice the EPA opposes, as doing so would bring the vehicle emissions out of compliance. Then there’s the safety issue — what if you run out of urea and the engine shuts down? That question is just the tip of the iceberg.
“In the school bus industry, the shops, they’re never big enough,” said Ed Mikelski, head mechanic for Wauconda CUSD and Diana’s husband. “There’s no wasted space. They’ll have to appropriate the space.

“And who will fuel? The mechanics? The drivers? Who will add the urea? How often do you have to do this? Every time you fill up? And does this last?”

Those answers are vital to the cost. Operators faced with the escalating prices of school bus equipment, parts and fuel are being forced to incorporate tighter, more efficient operating controls while pursuing technological options available to further optimize their student transportation program.

“Buses are ridiculously more expensive than when I became supervisor five years ago,” adds Wauconda’s Mikelski. “We’re trying to keep up by running newer models to eliminate the maintenance costs long-term, but it’s not easy.”