This week, the EPA has issued guidance on emission certification procedures for on-road diesels that use selective catalyst reduction (SCR) technology. What that means, in plain English, is that they will make it easier for manufacturers to understand and follow the guidelines. This is a particularly important event for Daimler-Chrysler and other manufacturers that have adopted the Bluetec urea-injection system for clean diesel. Previously, there were concerns that the EPA would frown upon any kind of emissions equipment that required replenishment (such as the urea cannisters). With this announcement, the EPA is making it clear that urea-injection or the use of other reducing agents is an acceptable strategy for clean diesel systems.
For Release: (Washington, D.C. -- Friday, March 30, 2007)
In a move that helps pave the way for putting more innovative and fuel efficient clean diesel cars and trucks on America's roads, EPA has issued guidance on emission certification procedures for on-road diesels that use selective catalyst reduction (SCR) technology. While SCR has been used successfully in other applications, this guidance enables automakers for the first time to adapt the technology to light- and heavy-duty vehicles on American roads.
SCR reduces emissions of the ozone-forming pollutant nitrogen oxide (NOx). It uses a nitrogen containing "reducing agent," (usually ammonia or urea) that is injected into the exhaust gas upstream of the catalyst. Drivers must periodically replenish the agent or else NOx emissions can greatly increase.
Manufacturers will need to gain approval for their SCR strategies as part of EPA certification. These strategies must address driver warning systems and inducement, system durability and reliability, and reducing agent quality and availability.
The March 27, 2007 letter is posted at: