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Catalytic Converter

While today's passenger cars emit 95% less pollution than similar cars did 25 years ago (before the catalytic converter was introduced), this is not so for typical sport utility vehicles (SUVs), minivans, or light trucks. Because they are not subject to the same emissions regulations, these vehicles can legally produce up to five times more pollutants than a passenger car can. Beginning in 2004, however, SUVs, minivans, and light trucks will have to meet the same standards that cars must meet — and they are tougher than the ones for today's automobiles.

This is good news for our environment. But not as good as it could be, because EPA standards primarily address pollutants that are emitted while a car is warmed up and running. They do not address the warm-up, or "cold-start," period, during which time today's cars and small trucks produce more than 50% of their emissions. The reason for so much emissions during the cold-start period is due to the fact that current-technology catalytic converters don't start to work until they reach a temperature of about 300°C (572°F). To reach this temperature, it typically takes about two minutes of operation. During those two minutes, the vehicle produces 60%-80% of its pollutants. Of all vehicle trips taken, 98% are within 24 hours of the previous trip. Conventional catalytic converters cool down within half an hour after the vehicle is turned off, which means for the great majority of trips, cold-start pollution occurs repeatedly.

This problem may soon be solved, thanks to NREL scientists. They helped develop a prototype catalytic converter utilizing compact vacuum insulation, phase-change materials, and variable conductance that can maintain its operating temperature 24 hours or longer, thus greatly reducing "cold start" pollution. And then they collaborated with Benteler Industries, which has licensed the catalytic-converter technology, to engineer a production-ready version. Compared to other concepts on the market, the new converter is cheaper, more versatile, lighter, and longer lasting. And it is the only one that deals with cold-start emissions.

Because of this new technology and of arguments put forth to the EPA, the new emission standards may very well take cold-start emissions into consideration. If they do, then the new standards could help reduce pollution by far more than an amount equivalent to immediately removing 107 million cars from the road — EPA's original estimate. The NREL/Bentler catalytic converter reduces emissions of carbon monoxide, hydrocarbons, and nitrogen oxides below the levels called for in the new standards.

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