Road Map to a Cleaner Diesel Drive

Change your oil according to your vehicle's maintenance schedule, and don't forget to fill the urea tank.

The urea tank?

Starting in 2010, owners of diesel-powered cars and trucks may have to fill a supplementary tank with urea, an organic compound that fights nitrogen oxide emissions when it's injected into a vehicle's exhaust system.

In anticipation of vehicle makers adopting an emissions-reduction system that depends on urea to meet tight diesel pollution-control rules, the Environmental Protection Agency issued guidelines on March 27 telling manufacturers how to earn certification for the new engines. The agency wants to ensure that urea is easily available and that systems will be designed to force owners to keep tanks full.

Besides offering insight into the EPA's concerns, the 10-page document illustrates how Washington's regulatory decisions can spawn applications of new technology, increase demand for a commodity and require the establishment of a supply and distribution infrastructure.

In this case, the industry's practical and engineering ingenuity is being challenged. Companies must design a system that would meet Clean Air Act rules by 2010 calling for the virtual elimination of nitrogen oxides and compel owners to maintain emission-control systems.

Diesel engine makers are looking at an advanced control device, called selective catalyst reduction, that uses a urea solution in the exhaust system, reducing the pollutant to nitrogen gas and water.

The technology is attractive to the manufacturers because it has worked in large industrial applications, is already used in Europe and is less costly than other approaches.

"The challenge is to scale it down," said Joseph Suchecki, a spokesman for the Engine Manufacturers Association in Chicago, which represents 29 major manufacturers of engines for trucks and industrial equipment.

The EPA doesn't doubt that the catalyst with a spritz of urea can do the job. Yet the agency wants to be sure that urea, now used largely as fertilizer, will be easily available and that vehicle owners will be prompted to use it.

Margo Oge, director of the EPA Office of Transportation and Air Quality, said the agency has "taken extra steps because we knew there were a number of issues" that companies using selective catalyst-reduction technology would need to overcome to meet nitrogen oxide standards.

The regulators' guidance suggests "driver inducement" as a way to get owners to pay attention to warnings that it's time for a urea refill.