It turns out our tendency to wrinkle our nose and hold our breath around diesel engines is a pretty good survival technique. Poor or inefficient combustion of diesel creates soot, the black smoke coming out of mufflers. The soot contains very small or nano particles.
Burning the sulfur in diesel creates sulfur dioxide and a tiny amount of sulfuric acid. The sulfuric acid droplets change and cling to nano particles. Minnesota Pollution Control Agency spokesman Mark Sulzbach says there's evidence the nano particles are a serious public health threat.
"These particles are so fine they can pass through the lungs into the bloodstream and affect the heart so it can cause even heart problems," he says.
Public health researchers say the diesel emissions are a factor in asthma, chronic bronchitis and may be responsible for as many as 20,000 premature deaths a year in this country. The new rules bring the sulfur levels in diesel down from 500 to 15 parts per million.
This is welcome news to diesel advocates who point out the positives. Diesel engines are more efficient. A gallon of diesel goes further than gasoline, thus, a diesel powered engine produces less carbon dioxide, a greenhouse gas.
Overnight a switch to this ultra low sulfur diesel fuel means that every diesel tailpipe will be about 10 percent cleaner. Overnight.Richard Kassel, Natural Resources Defense Council
Richard Kassel, an attorney with the Natural Resources Defense Council, says next year another set of federal rules take effect which limit emissions from diesel engines. The new ultra low sulfur diesel rules Kassel says, pave the way for new diesel technology.
"Overnight a switch to this ultra low sulfur diesel fuel means that every diesel tailpipe will be about 10 percent cleaner. Overnight. And then when a trucker or bus fleet buys a new engine starting next year that new engine will be 90 percent cleaner than the one it replaces," he says.
Experts estimate diesel powered vehicles account for less than 10 percent of the cars and trucks on the road. However most of the nation's larger over-the-road trucks are powered by diesel. Nearly all heavy construction equipment burns diesel, and most of the country's school buses burn the fuel.
The pollution created in urban areas, experts say, is disproportionately large to the number of vehicles. Air samples from around the country including the Twin Cities show nearly half the health threatening fine soot particles are from diesel emissions.
University of Minnesota mechanical engineering professor David Kittelson, a world renowned expert in diesel and biofuels technology, says nearly everyone will notice one effect of burning ultra low sulfur diesel.
"You're not going to see any clouds of smoke coming out of diesel trucks in the future," he says.
According to Kittelson, by next year what little soot is created by the combustion will be captured by catalysts and filters.
"The emissions are so low that the exhaust gets down to where it's almost indistinguishable from ambient air," he says.
This is welcome news for car makers. The new ultra low sulfur diesel helps them meet air emission standards. Jeep and Mercedes Benz, for example, have diesel powered models ready for the showroom. They'll meet emission rules in 45 states but not in California and a handful of others which have even stricter standards.
However, Kittelson says carmakers attraction to diesel is driving them to create ever cleaner diesel vehicles. He says in 2009 Honda will introduce a diesel powered passenger car that meets California rules.
For the present there's still a problem. Diesel engines have extremely long lives.
The beneficial effects of the cleaner ultra low sulfur diesel will be slowed because it will take truck and bus fleet owners up to 30 years before they buy new vehicles. Congress has approved tax credits to speed the changeover.
Environmental groups, including the Minnesota Environmental Initiative, are acting on their own. Through the MEI's Project Green Fleet, a voluntary program, it is working with school districts to retrofit the state's thousands of diesel burning school buses.