Road Map to a Cleaner Diesel Drive

The agency suggests visual and possibly audible alarms that would escalate in intensity as the storage tank approaches empty, "culminating in driver notification that cannot be defeated or ignored." The EPA says an "inducement mechanism" may include one that makes drivers unable to start the vehicle.

The EPA cautioned that the systems must be designed so they can't be disabled, tampered with or filled with something other than the proper concentration of urea. And the agency wants urea to be available at dealers and truck stops, as well as at auto and convenience stores.

"It places a lot of the burden in the laps of engine manufacturers that there never be an empty tank of urea," said Glen Kedzie, assistant general and environmental counsel for the American Trucking Associations, an Alexandria group that represents trucking companies. Yet he said no one wants to see a trucker put in an unsafe position, stranded in the middle of nowhere without urea.

To respond to the challenge, the companies involved in efforts to control diesel pollution have formed the Urea Distribution Stakeholder Group, which meets monthly in Washington.

"It's kind of a chicken-and-egg thing," said Steve Namanny, manager of North American sales at Terra Industries in Sioux City, Iowa, which makes about 1.3 million tons of urea liquid annually in five plants. "We are ready to support it."

Petroleum marketers expect demand will determine the extent of investment in storage infrastructure. Dan Gilligan, president of the Petroleum Marketers Association of America, said one concern is keeping the urea warm enough because it freezes at 11 degrees Fahrenheit.

Environmental groups that battled for diesel-emission reductions want to see the rule implemented on schedule.

"It's an important thing to make sure trucks are clean," said Frank O'Donnell, president of Clean Air Watch, a nonprofit group in Washington. "It eliminates one of the biggest sources of pollution plaguing us for decades."

The economic payoff from a change in the image and performance of diesel engines is expected to be sales of more expensive truck engines and passenger cars that are quieter, fuel efficient and an alternative to hybrid-vehicle technology.

Diesel has long been the power source of choice for larger rigs. Yet motorists have been uninterested because diesels were regarded as dirty, noisy and sluggish.

Allen Schaeffer, executive director of the Diesel Technology Forum, a group of engine manufacturers, refiners and makers of emission-control technology, said about 10 percent of new passenger vehicles will be diesel-powered in the next decade. In 2005, 3.6 percent of new passenger vehicles were diesels, including light trucks.

Automakers such as DaimlerChrysler, Honda, Volkswagen, BMW and General Motors are working on diesel technology, some of which will be urea sippers. The diesel forum's Web site showcases more than a dozen cars, sport-utility vehicles, small trucks and vans that use a variety of diesel-pollution controls.

Mercedes-Benz, which is owned by DaimlerChrysler, sells four "clean" diesel models in the United States that run on ultra-low-sulfur fuel. Next year, it will roll out three SUVs that will use the urea-based solution, qualifying the vehicles to be sold even in states like California with the most stringent emission standards.

Cindy Skrzycki is a regulatory columnist for Bloomberg News. She can be reached atcskrzycki@bloomberg.net.