DETROIT - Diesel-powered vehicles that rely on a controversial chemical called urea to lower tailpipe emissions are closer to getting a green light from the EPA.
At least one automaker appears to have developed an early-warning system that satisfies EPA regulators that drivers won't let their vehicles run out of urea - and violate emissions limits as a result.
When a car is out of urea, it won't meet emissions standards until the chemical is replenished. That has been a major hang-up for the EPA. All other emissions systems are passive and require no maintenance by the driver.
"We have at least one company that has presented ideas that we think are workable," Margo Oge, the EPA's director of the Office of Transportation and Air Quality, told Automotive News.
Oge declined to name any automakers or talk about what technologies have been shown or discussed.
Preventing the car from starting when the urea runs out appears to be out of favor. "People are thinking creatively and in a way that there won't be any safety issues. Getting stuck on the road I don't think is the solution," Oge said.
"There are a lot of technological ideas that the (auto) companies have that will allow the cars to work only when urea is in the vehicle," she said. "So we are pretty optimistic that if the companies decide to take the urea approach, the technology will work."
The urea method, also called selective catalytic reduction, or SCR, is the most promising emission technology that enables diesel engines to meet stringent Tier 2 EPA standards. Tier 2 requires diesel engines to run as cleanly as gasoline engines. The regulations will be phased in fully by 2009.
Urea injection systems clean oxides of nitrogen, or NOx, from the exhaust. Not only does the method work, but it costs far less than particulate filters and traps in the exhaust. SCR does not affect engine performance.
Five automakers have said they are working on urea systems. They are DaimlerChrysler, Ford Motor Co., General Motors, BMW and Volkswagen.
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