EPA Issues SCR Guidelines

The Environmental Protection Agency said last week that diesel engine manufacturers who want to use selective catalytic reduction to meet EPA’s 2010 emission rules must supply the urea SCR requires and prove it will be available to truck drivers using those engines.
In a March 29 letter to engine makers providing guidance for obtaining EPA certification for the new engines, the agency also said original equipment manufacturers would have to design warning systems to disable an SCR-equipped truck if a driver attempted to bypass emission controls, for example, by not refilling the truck’s urea tank.
“The two most important parts of our guidance are the recommendations for driver warning systems and urea supply,” said EPA spokesman John Millett, adding that the agency will be “focusing on those two areas as we certify SCR engines.”
“We have to look at the plans in place from truck makers, to ensure that once the vehicle is on the road, it continues to meet tough new emissions standards,” Millett said. “This guide gives the manufacturer a clear idea of what EPA is looking for.”
SCR uses urea as a reducing agent that enables catalytic converters to break down nitrogen oxides in diesel exhaust. Several engine manufacturers have said it is the most promising technology available to meet EPA’s stringent 2010 standards.
Millett said EPA did not specify what reducing agent manufacturers should use, or how often that reducing agent should be refilled in an engine, adding that the guidelines “are fuel and technology neutral.”
EPA laid out a two-part certification plan outlining the requirements manufacturers must meet to sell SCR engines. While EPA’s letter is not a formal rule, manufacturers must receive EPA certification before they can sell new engines.
“It will be important for manufacturers to demonstrate, either individually or as part of a collective effort, that it will be reasonable for truck operators to obtain reductant at truck stops or other fueling locations when they stop to refuel,” said EPA.
SCR technology would require an infrastructure to allow “widespread distribution” of urea across the United States, including “convenient availability . . . at locations that are easy to find,” EPA said.
EPA said in its SCR guidance that engine manufacturers should supply urea at dealerships and through a “back-up” toll-free phone number truckers can call if they need urea but are unable to find it.
EPA said manufacturers should use a system of lights on the truck dashboard or messages displayed in a vehicle message center to inform “the vehicle operator [when the] reducing agent level is low and must be replenished.”
Such a warning system could also have an audible alarm that would escalate in intensity as the reducing agent’s tank approached empty, culminating in a warning “that cannot be defeated or ignored,” EPA said.
Engine manufacturers also must develop a secondary warning system “onerous enough to ensure that users will not operate the vehicle without reducing agent,” EPA said.
The secondary system would prevent drivers from refueling and slow down a truck’s engine if the first warning system is ignored.
EPA suggested several methods of preventing a driver from bypassing emission controls by operating an SCR-equipped truck without urea or with an incorrect reducing agent.
In the first scenario, a truck driver would be allowed to start the engine a limited number of times without urea before “the vehicle is unable to restart without the [urea] tank being replenished.”
A separate scenario would “lock-out” a truck driver by “preventing the user from being able to refuel the vehicle after the [urea] drops below a certain level,” EPA said.
Another way to make sure vehicle operators are adding reducing agent “is to have vehicle performance degraded in a manner that would be safe, but onerous enough to discourage the user from operating the vehicle until the reducing agent tank was refilled, EPA said.
Chris Patterson, chief executive officer of truck maker Freightliner LLC, which plans to use SCR, told Transport Topics March 21, “We don’t see any problems at all of having enough urea distribution points in 2010. It is needed and, one way or another, companies that sell fuel to truckers will find ways to get urea.”
Similarly, Othmar Stein, director of communications for Freightliner parent DaimlerChrysler — also speaking before EPA released its guidelines — said neither his company “nor any other trucking firm had trouble with the availability of urea when SCR technology was adapted in Europe. Some truck stops had fuel trucks initially to disburse it, others had aboveground small tanks and many fleets built their own underground tanks.”
Patterson said Class 8 trucks “will probably need to fill up on urea about every third time that they stop for fuel.”
Besides Freightliner, Volvo Trucks North America and Mack Trucks have announced they will use SCR to meet EPA’s 2010 emission standards, which cut emission levels sharply from the 2007 levels.
Other manufacturers including International, Paccar, Cummins and Caterpillar have not yet announced whether they will use SCR.
Staff Reporter Frederick Kiel contributed to this story.