With the federal government's 2010 truck emission mandates looming, refuse truck fleets need to start thinking about exhaust control technology.

Every diesel engine maker and truck manufacturer except Warrenville, Ill.-based Navistar Corp. is planning to use selective catalytic reduction (SCR) technology to reduce the amount of nitrogen oxides (NOx) given off in the exhaust stream down to the required level — 0.2 grams per brake horsepower hour(g/bhp-hr), a truly miniscule amount.

Navistar, on the other hand, will use what it calls advanced exhaust gas recirculation (advanced EGR) to cut NOx emissions from its MaxxForce brand of diesel engines down to the required level.

All heavy-duty diesel engines, except for those built by Peoria, Ill.-based Caterpillar, use EGR. It's just that Navistar's product line will use more of it, along with higher fuel injection pressures and other measures, to reach the required level. Caterpillar found the technology investments to make its truck engines compliant with the 2010 federal emission regulations too expensive, so it's exiting the truck engine market.

Mike Delaney, senior vice president of marketing for Portland, Ore.-based Daimler Trucks North America (DTNA), which builds Freightliner-brand trucks and also owns engine maker Detroit Diesel Corp. (DDC), Redford, Mich., says the biggest benefit of SCR is improved fuel economy. Exactly how much improvement a fleet can expect remains to be seen, but "if an engine system can deliver even a 1 percent or 2 percent increase in fuel economy, it would save a significant amount in diesel," says Jeff Jones, vice president of sales and marketing for Columbus, Ind.-based engine maker Cummins Inc.

"Depending on the cost of diesel fuel, you could expect a return on the SCR technology in less than three years with fuel savings alone," says David McKenna, powertrain sales and marketing manager for Greensboro, N.C.-based Mack Trucks, which is owned by Sweden's Volvo AB and aligned with Volvo Trucks North America, also based in Greensboro.

However, according to a study by New York-based NERA Economic Consulting and supported by Navistar, 2010-compliant Class 8 trucks using SCR systems could cost $7,000 to $10,000 more than today's vehicles. Engine makers using SCR dispute those numbers, but they do admit price increases for SCR-equipped trucks are inevitable. Bernard Heil, Daimler's VP of truck product engineering powertrain, noted that SCR added some $4,000 to the cost of European commercial trucks.

Even though SCR reduces diesel fuel consumption, it requires diesel exhaust fluid (DEF), which is made from the liquid ammonia compound urea, to be sprayed into the tailpipe in order to do so. Furthermore, Navistar says DEF won't be cheap.

"We believe urea is a secondary fuel that will have a cost that will be at least as much as diesel," says Bob Carso, director of global brand strategy for Navistar's engine group. "We have data showing, at the retail level, it's extremely expensive. We have paid $19.04, including tax, for a half-gallon of DEF in a packaged scenario."

Those engine OEMs using SCR, however, say DEF costs won't be anywhere near that expensive. In a recent truck emissions forum hosted by the Environmental Protection Agency (EPA), both Volvo and Mack stated that DEF should cost about $2.70 per gallon — and, with roughly two or three gallons of DEF required per 100 gallons of diesel fuel consumption, the costs should be minimal for truck fleets.