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Pollution Patrol

In November, Professor Don Stedman drove his mobile lab --an RV jammed with equipment -- to Phoenix to monitor emissions of some 25,000 automobiles a day. Photo: Michael Richmond

“Beam me clean!” proclaims the green and white bumper sticker that adorns the outside window of Don Stedman’s office in the Seeley Mudd Building. It’s a fitting sentiment for the Brainerd F. Phillipson Professor of Chemistry, for he has devoted his career to separating “clean” vehicles from dirty ones with beams of light.

He’s studied the exhaust spewing from planes, trains and automobiles, as well as trucks, snowmobiles and even motorized tricycles. His research has resulted in more than 10 patents and has challenged conventional thinking about air pollution, created a new model for automobile emissions testing and earned him both accolades and enmity.

Working toward a cleaner future

Stedman started his career “studying reactions of gas-phase atoms and molecules that very few people in the world cared about,” he quips. After graduate school, he did research for Ford Motor Co. just as the Clean Air Act was focusing automakers’ attention on photochemical smog and auto exhaust. After two years with Ford, he joined the University of Michigan faculty in the departments of chemistry and oceanic science.

“It was becoming obvious that our modeling of the atmosphere was suffering from poor inputs,” he recalls. To address that problem, the University of Michigan’s Lucien Chaney was trying to measure carbon monoxide with a spectrometer.

Spectrometers gauge how matter interacts with the electromagnetic spectrum. The most familiar section of the spectrum is the rainbow-like swath of color revealed by a prism. Other sections include radio waves, X-rays and infrared light, each of which travels through space at a different wavelength. Because different elements absorb different wavelengths, it’s possible to identify an element by determining which wavelengths pass through it and which don’t.

“When you see smoke coming from an exhaust pipe, you are seeing the light absorbed from the sky,” Stedman explains. “You’re doing real-time spectroscopy with your eyeball.”

When Chaney finally got his spectrometer working in 1976, he turned to Stedman for ideas about what to do with it.

“I said, ‘Let’s take it outside and shoot it across the street,’ and we found we could measure carbon monoxide from passing vehicles,” Stedman recalls.

That experiment led to the development of the Fuel Efficiency Automobile Test (FEAT) at the University of Denver 10 years later. A remote sensor for measuring the tailpipe exhaust of moving vehicles, FEAT was created in 1987 with a grant from the Colorado Office of Energy Conservation.

Stedman designed and built the first model, FEAT 1000, with help from the physics department and the University of Denver Research Institute. Research Engineer Gary Bishop created the software.

FEAT components straddle a single-lane roadway or highway ramp. An infrared light source on one side shines a beam through the exhaust stream of a passing vehicle to a detector, calibration device, computer and video camera on the opposite side. When a car passes, FEAT analyzes fumes issuing from the tailpipe and takes a video reference picture of the license plate. DU scientists currently are developing bridge-mounted sensors to monitor multiple lanes from above.

The early model could measure only carbon monoxide and carbon dioxide. Knowing the amount of each gas alone doesn’t yield useful information, Stedman explains. But knowing the ratio of the two tells scientists volumes about how cleanly the engine is running, how efficiently it’s burning fuel and whether it needs a tune-up.

“It worked better than we ever thought — it was unbelievable,” he says enthusiastically. “It turned out that it was successfully measuring the carbon monoxide emissions from over 90 percent of the passing cars, and we would have been happy with 10 percent.”

And it was doing it for just pennies per test. Douglas Lawson, a principal scientist at the National Renewable Energy Laboratory in Golden, Colo., collaborated with Stedman on several studies during the 1980s, when Lawson worked for the California Air Resources Board.

“His work corroborated work I had been involved with in California, where we were saying something was dreadfully wrong with our knowledge of mobile emissions,” Lawson recalls. Lawson, in turn was able to document FEAT’s accuracy at measuring carbon monoxide emissions.

“We’ve pretty much been lockstep with each other, but using different methods in a variety of studies,” Lawson says.

Starting the in the late 1980s, the EPA Remote Sensing Group in Las Vegas funded several FEAT demonstration studies around the country. “FEAT 1000 could measure 10,000 cars per day, but it was still research and demonstration — it wasn’t anything that was going to go commercial,” Stedman explains.

So the team began to develop improved models featuring state-of-the-art infrared detectors that could handle roadside conditions and still collect 100 samples per second. The number of detectable chemicals grew to include hydrocarbons, nitrogen oxides, and more recently, sulfur dioxide and ammonia.

A long list of sponsors — including the National Science Foundation, California Air Resources Board, the Colorado departments of health and transportation, Ford Motor Co., General Motors Corp., Coordinating Research Council, National Park Service, Environmental Systems Products and major oil companies — have funded measurements all over the world. The studies are chronicled in more than 100 scientific papers and thousands of mentions in the mainstream news media.

As the data accumulated, unexpected patterns began to emerge. Contrary to the widespread assumption that every vehicle contributes significantly to air pollution, it became clear that a small number of particularly dirty vehicles cause most of the problem. Stedman dubbed the offending vehicles “gross emitters.”

“When we started, I don’t think anyone knew that half the emissions came from only 10 percent of the cars,” he says. “Today, half the emissions come from only 5 percent of the cars. We were very successful in getting the message out that gross polluters are there, and if you don’t fix them you are wasting your time [with other anti-pollution measures]. It’s been harder to get the message out that the vehicles can be easily identified by this technique and that could be the most efficient route to getting them fixed.”

As automakers have developed cleaner cars, the percentage of gross emitters has continued to drop, he adds. Today, one in 25 cars emits more pollutants than the others combined.

Since 1988 Stedman has advocated “dirty-screening” using remote sensors to single out the worst polluters and force them to fix or retire their dirty vehicles. Meanwhile, the rest of us would be excused from the long lines and annual fees associated with mandatory emissions tests. This idea earned Stedman the scorn of people with a vested interest in mandatory inspections, including the testing industry, regulators and even environment purists. Though he was labeled a crackpot, he persisted in promoting the virtues of dirty-screening.

“When only a few hundred out of any 5,000 cars need to be fixed, it just jumps out at me that you shouldn’t worry about the other 4,800. I’m arguing that the top 50 are really the most important,” he explains. “I got a terrible reaction from floating that idea because a lot of people make a lot of money testing cars at $25 per test.”

Lawson, who is a member of the Colorado Air Quality Control Commission, agrees. “The state and the emission testing contractor don’t want this program to end because they derive a lot of money from it,” he says, noting that remote sensing has been an important tool for demonstrating why progress in improving air quality has been so slow.

Finally, in December 2005, Colorado Gov. Bill Owens and Doug Benevento, executive director of the Colorado Department of Public Health and Environment, called for an end to vehicle emissions tests in the Denver metro area. Even the Environmental Protection Agency, a staunch testing booster, is reconsidering. Richard Long, head of air programs for the EPA’s Colorado regional office, was quoted in the Rocky Mountain News saying the programs “may have outlived their usefulness.”

Even so, the mandatory inspection program is still in place.

“We have serious problems in Colorado,” Lawson says, noting that the state could easily fail EPA attainment standards for ozone unless it gets serious about fixing or eliminating gross emitters. “The low-hanging fruit for the urban emission reduction program nationwide is high-emitter cars,” he says. “And remote sensing is the silver bullet because it can quickly find them.”

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