Engine Makers Defend SCR Against ‘Unsubstantiated Claims’
This story appears in the March 2 print edition of Transport Topics.
Truck engine makers planning to use selective catalytic reduction in 2010 engines lashed out last week against what one executive called “unsubstantiated attacks leveled against SCR” by the one manufacturer that plans to use only exhaust gas recirculation to cut emissions of smog-forming nitrogen oxides.
Scott Kress, senior vice president of sales and marketing for Volvo Trucks North America, said customers have been confused by what he called “smoke and mirror tactics” that distract from the “reality” that “half a million” SCR trucks are in service worldwide.
Kress and Volvo drivetrain manager Ed Saxman spoke in a Feb. 23 meeting with Transport Topics editors, during which Kress said, “You can tell we’re a little frustrated about what people are saying.”
Kress said one manufacturer plans to use “heavy EGR” and that to meet EPA’s 2010 NOx mandate, “is driving EGR to the limits with an essentially new engine.”
Of the major truck OEMs in the U.S. market, only Navistar Inc., maker of International trucks, plans to use EGR exclusively to produce the sharp drop in NOx that EPA’s 2010 mandate requires.
Navistar’s EGR-only 2010 engine is “an untested approach,” Kress said.
EGR reduces NOx by circulating exhaust gas back into the engine to cool combustion, while SCR injects urea-based diesel exhaust fluid into exhaust to help an aftertreatment catalyst change NOx into water and nitrogen.
In a separate talk last week with TT, Detroit Diesel Corp. Director of Marketing David Siler said, “We see some myths and unfounded statements out there” about SCR.
Detroit Diesel makes engines for Daimler Trucks North America’s Freightliner and Western Star brands.
Officials of Volvo, which also makes engines for Mack Trucks, said no engine maker in the world has met emission standards as strict as EPA 2010 without an SCR system.
As SCR’s North American debut draws nearer, concerns about the availability, stability and cost of DEF have become the cornerstone of what Daniel Ustian, Navistar’s chief executive officer, dubbed “the risks of an SCR strategy.”
But the representatives of both Volvo and Detroit Diesel dismissed concerns Navistar raised.
Saxman saw no supply problem for urea, which mainly is used as fertilizer. “If all the U.S. and Canada went to SCR overnight, it would bolster total urea demand by 2%.” He added that “within the coming year, all major truck stops will have DEF available.”
Pilot Travel Centers and TravelCenters of America, two of the largest U.S. truck stop chains, have said they will sell DEF in containers and Pilot said it will begin installing bulk DEF distribution this year.
Volvo and Detroit Diesel also refuted Navistar‘s argument that DEF stored onboard a truck would freeze in cold weather.
Kress acknowledged that DEF gets slushy at about 12 degrees Fahrenheit, but said “DEF freezing is not a major concern,” because Volvo’s SCR tanks have a heater, so a truck that has been parked outside over a cold weekend can be started and driven off without delay.
Daimler’s trucks will also have an in-tank heater, Siler said.
Neither Volvo nor Detroit Diesel would speculate in detail on the price of DEF in the United States, but said Navistar has greatly exaggerated the price.
Kress said that Volvo expects “a net savings using DEF,” because SCR improves fuel efficiency 3% to 5% compared with current engines.
Siler said that those savings include higher resale value for trucks using SCR because the engines won’t be stressed as much as those using EGR.
“We think SCR trucks will deliver better resale value [because] they’re running more efficiently,” Siler said. He argued that SCR engines produce less soot and require fewer active regenerations of their diesel particulate filters than do enhanced EGR engines.
“Active regeneration” refers to burning accumulated soot in the DPF to prevent filter clogging, but it consumes diesel.
A Navistar representative agreed that SCR engines may get better fuel economy, but rejected the idea that enhanced EGR would result in more soot, additional DPF regeneration, or less-efficient engines.
“We don’t accept the premise that we’re going to make more soot,” said Tim Shick, Navistar’s director of business and product strategy.
“We don’t produce more soot because of higher injection pressures [and] DPF regeneration won’t occur more frequently,” he added.
Shick said that Navistar’s 2010 engines will use a high-pressure, common-rail fuel injection system to deliver a finer mist of diesel into engine cylinders, increasing the surface area of combustible fuel and allowing for a more complete burn.
Shick told TT “we would dispute that you would have lower operating costs when DEF is a part of the cost. We don’t know what independent retailers would sell it for, and we submit that [SCR proponents] don’t either.”
Navistar said its EGR-only system will reduce NOx emissions to .5 grams per brake horsepower-hour. To meet EPA’s 2010 standard of .2 g/bhp-hr of NOx,
Navistar will draw on credits it accumulated by exceeding earlier EPA emission standards.
Volvo and Daimler said they would meet the EPA standard without using credits.
