The Environmental Protection Agency is revisiting its guidance for selective catalytic reduction technology in heavy-duty trucks as a result of a court settlement with Navistar Inc. earlier this year, an agency official said recently.
“We’re working on new guidance,” Margo Oge, director of EPA’s Office of Transportation and Air Quality, told Transport Topics on Oct. 19 here during the Clean Diesel 10 conference.
Oge would not say whether the revised guidance would require engine manufacturers that use SCR to increase the severity of the engine derating that occurs when a truck runs out of diesel exhaust fluid, the liquid additive used to scrub nitrogen oxides from engine exhaust.
She also declined to say when the new guidance might be published, but Patrick Charbonneau, Navistar’s vice president of government relations, told TT the guidance could be issued as soon as January.
Other truck and engine makers attending the conference, which marked the 10th anniversary of EPA’s clean diesel rules, declined to comment on EPA’s guidance plan. However, they did say stricter derating requirements could be implemented easily.
Altering derating parameters “is a software change,” said Brian Mormino, director of energy policy for engine maker Cummins Inc., Columbus, Ind.
Although Brad Williamson, manager of product marketing for Daimler Trucks North America, said changing derating settings would require engineers to spend many hours testing software changes and verifying their effectiveness, he agreed the company could easily adjust to any mandated changes.
Calls to Paccar Inc. and Volvo Trucks North America for comment were not returned by press time.
Currently, when an SCR truck runs out of DEF, visual and audio alarms alert the driver, and the truck’s engine power is gradually reduced. Eventually, if a driver takes too long to replenish the DEF reservoir, the engine is limited to a maximum speed of about 5 miles per hour.
These derating parameters were instituted by engine makers after EPA agreed in 2007 that SCR could be used to meet the 2010 emission cuts — provided that safeguards were established to prevent trucks from running without DEF.
EPA outlined these safeguards in an SCR guidance document, which said that engines should be derated if a truck ran 2,000 miles or 40 hours without DEF. Earlier this year, in response to Navistar’s lawsuit, EPA removed from its guidance all time and mileage limits for running without DEF. The agency said it wanted to avoid giving manufacturers the impression that the guidance was legally binding.
Navistar, the only truck maker using exhaust gas recirculation technology — rather than SCR — to meet EPA’s 2010 standards, maintains any engine derating short of a complete shutdown allows trucks with SCR systems to operate illegally.
Navistar has attacked SCR technology aggressively, both in the marketplace and in the federal court system, drawing the ire of competitors.
Over the summer, Navistar said an independent study it commissioned showed that SCR trucks can run even when their DEF reservoirs are empty or filled with tap water.
Navistar’s claim prompted a scathing rebuke from Daimler Trucks North America, published Aug. 9 as an advertisement in Transport Topics, in which that company accused Navistar of “fear-mongering, deception and distraction.”