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April 30, 2007 8:00 AM, EDT

EPA Stance on SCR Earns Praise

Details Still Cause Concern

By Andrea Fischer, Staff Reporter

This story appears in the April 30 print edition of Transport Topics. Click here to subscribe today.
Truck and engine makers said they were pleased with new guidelines on selective catalytic reduction technology issued by the Environmental Protection Agency last month, despite lingering concerns over how urea sensors and driver warning systems will work on SCR-equipped trucks.
“We are convinced that SCR is the best choice for continuing to dramatically re-duce diesel engine emissions in 2010 while delivering optimal performance and fuel efficiency . . .” Peter Karlsten, president of Volvo Trucks North America, said in an April 23 statement.
“The EPA has provided an important guide for the many stakeholders working to address the urea infrastructure and other issues necessary to bring this clean-diesel technology to the North American market,” he said.
Engine maker Caterpillar Inc. has not yet announced what technology it will use for its 2010 engines, but, “in general, we’re happy with the [EPA] guidance,” Gordon Gerber, engine emissions manager, told Transport Topics in an interview.
However, he cautioned, “there are concerns in terms of how the EPA has structured the guidance document in relation to measuring the urea quality and level of urea” in the engine.
“The issue [of urea sensors] is certainly not insignificant. [Manufacturers] have issues to overcome there,” Gerber said.
Paul Vikner, president of Mack Trucks, praised the agency’s guidance, saying, “This document is a critical guideline” for manufacturers.
Volvo and Mack are sister companies within Volvo AB. The two companies announced last year that they would use SCR technology to meet 2010 federal emission standards.
Manufacturers will have to  receive EPA certification before they are allowed to sell SCR-equipped engines to meet the 2010 regulations.
In a March 29 letter providing guidance for obtaining EPA certification for the new engines, the agency said original equipment manufacturers would have to design sensors to monitor the quality and quantity of urea, an essential component of an SCR system (4-2, p. 1).
“We’re happy with the EPA guidance. There has to be a structure out there to develop this technology, and EPA has provided that,” said Chuck Blake, senior technical sales support manager for Detroit Diesel Corp.
Freightliner LLC, Detroit Diesel’s parent company, also announced last year that it would use SCR-equipped engines to meet 2010 requirements.
However, said Blake, “We think onboard diagnostics systems for urea will be a challenge to develop. We can get over it, but it will definitely be a challenge.”
Freightliner is a part of DaimlerChryler AG. Both Daimler and Volvo are based in Europe, where SCR already has developed a following in truck manufacturing.
Christine Vujovich, vice president of marketing for Cummins Inc., said, “This information is consistent with the spirit of our discussions we have had with EPA on this subject.”
Cummins has not announced a decision on 2010 technology, nor have International Truck and Engine Corp. and Paccar Inc., which declined to comment on EPA’s guidance.
SCR uses urea, an organic compound based on nitrogen, as a necessary reducing agent that enables catalytic converters to break down nitrogen oxides in diesel exhaust.
Looking ahead, EPA spokesman John Millet said last week the agency will focus on urea supply and driver warning systems “to ensure that, once the vehicle is on the road, it continues to meet” emission standards.
Millet said the agency is having discussions with manufacturers as they begin to determine how those systems will work.
“This is an example of working together to achieve the right environmental and economic outcome,” said Millet.
But Caterpillar’s Gordon Gerber said there are no commercially available sensors that could determine whether or not an SCR system is using urea currently on the market.

“We need to come to an industry agreement on how to manage SCR systems in general,” said Gerber.
In its guidance, EPA said manufacturers should place a sensor in the truck engine or exhaust stream to ensure that urea is working correctly to reduce nitrogen oxides.
EPA also said manufacturers would have to design warning systems to disable an SCR-equipped truck if a driver attempts to bypass emission controls by not refilling the truck’s urea tank or by refilling it with a substance other than urea.
“These are all issues we are still trying to figure out,” said Will Schaefer, staff engineer for the Truck Manufacturers Association. “The EPA guidance is a good start, but there needs to be an industry consensus in terms of how a driver will fill up a urea tank and how the truck and engine systems manage urea. There is a feeling that this should be as user-friendly as possible and consistent across all brands of trucks.”