The Environmental Protection Agency is considering a variety of rules that it might apply to urea injection for diesel engines, and is said to ready to issue rules for such emission-control devices in upcoming weeks. The regulations are expected to address potential issues arising with urea injection, such as the availability of the substance, making sure that the system and its low-fluid-level warning system are tamperproof, and dealing with urea's freezing point of 11F. One of the largest areas of contention between the EPA and automakers involves a proposed interlock between the urea level-monitoring system and the engine that would perhaps disable the starter or lock the vehicle's fuel cap if urea levels drop too low to ensure proper function.
Starting in 2010, all diesel vehicles sold in the US must meet or exceed "Bin 5" classification of the Tier II clean air standards, which would effectively make oilburners as clean as gasoline engines. Urea injection helps reduce the level of oxides of nitrogen when injected into the tailpipe, and does so at a cost perhaps 10% lower than the competing NOx trap technology. Bosch sees the combination of urea and selective catalyst reduction as the path toward diesel cleanliness, and GM has shown off the technology on a diesel light-truck prototype. VW's emission certification problems with the diesel Touareg last year elevated the profile of urea injection - and the problems surrounding it - here in the United States, and prompted the EPA to start moving.
[Source: Autoweek/Automotive News]