Earth Talk: Large Trucks Contribute Half the Soot in the Air

Earth Talk
Large Trucks Contribute Half the Soot in the Air

Dear EarthTalk: Are there any efforts underway to lessen the environmental impact-which must be considerable-of all the "18 wheelers" and other large vehicles that are numerous on our highways? -- Sadie Strauss, Madison, WI
According to the Union of Concerned Scientists, although large trucks account for just six percent of total highway miles driven in the U.S., they are responsible for a host of environmental threats. These include over half the soot and a quarter of the smog-causing pollution generated by highway vehicles, six percent of the nation's global warming pollution, and more than a tenth of the country's oil consumption.
A typical diesel-powered 18-wheeler can emit as much nitrogen oxide and fine particulates-key elements in the formation of asthma-inducing smog-as about 150 passenger cars. Although strict limitations on emissions of various pollutants from cars have been in place in the U.S. since the 1970s, trucks and other large transport vehicles have been allowed to emit as much as five times as much pollution per mile.
But thanks to new regulations put in place by the U.S. Environmental Protection Agency (EPA), new trucks coming off assembly lines in the years immediately ahead promise to be much cleaner and greener. Known collectively as the EPA's Heavy-Duty Highway Diesel Rules, the new regulations mandate that trucks manufactured in 2007 or after produce 75-90 percent less nitrogen oxide and 90 percent fewer particulates than earlier models. Of course, with most of the trucks on the road made prior to 2007 and thus exempt from the new regulations, air quality improvements won't happen overnight.
In the meantime, though, the federal government has also instituted new regulations mandating that diesel fuels contain 97 percent less sulfur, another primary component of smog, than previously required. This means that all diesel-powered vehicles in the U.S., new or old, will be polluting less. Regulators hope that the combination of greener trucks and cleaner fuel will eventually bring emissions from large trucks into parity per mile driven with cars and light trucks (SUVs, pickups and minivans).
Beyond making existing truck engines more efficient, new technologies promise to green the trucking industry even more. Biodiesel, a form of diesel fuel derived from renewable plant crops, is coming on strong. According to the U.S. Department of Energy, use of the most common blend, B20 (80 percent regular diesel and 20 percent biodiesel), cuts petroleum use by 19 percent, greenhouse gas emissions by 16 percent and hydrocarbon emissions by 20 percent.
Also, hybrid technologies popularized by the Toyota Prius are starting to show up in trucks. Federal Express is pioneering the use of hybrid technology in trucks by outfitting many of its new delivery trucks accordingly. And several U.S. cities now run hybrid diesel-electric buses. Environmental leaders hope such fuel- and emission-saving technologies will trickle down into the private trucking industry as well.

Contacts: Union of Concerned Scientists, www.ucsusa.org; EPA's Heavy-Duty Highway Diesel Program, www.epa.gov/otaq/highway-diesel.
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