For the study, part of a five-year project, heavy-duty diesel engines from the four major manufacturers--Cummins, Detroit Diesel, Caterpillar and Volvo-- were tested for more than 300 air pollutants at a laboratory in San Antonio, Texas. The researchers only tested new engines, so the trucks and buses might put out more emissions as they age, Greenbaum said. But under the EPA rules, their warranties for emissions equipment must last 450,000 miles, four times longer than cars.
Greenbaum said one surprise was the extent of reductions in cancer-causing and other toxic compounds. Diesel exhaust is considered a potent human carcinogen because of a variety of substances. Polycyclic aromatic hydrocarbons declined 79 percent from 2004 models, while elemental carbon and metals were down 98 to 99 percent.
The challenge in cleaning up diesel has been finding technologies that can trap particles and gases without reducing fuel efficiency. Spurred by new standards adopted by California and the EPA, the engine manufacturers and oil industries had to develop ultra-low sulfur fuel and new catalysts and other gas-control technologies.
Controlling nitrogen oxides, or NOx, has been the biggest challenge. EPA’s rule for 2007 engines, adopted in 2000 by the Clinton Administration, gave manufacturers three extra years for fully meeting that standard. “The original rule basically recognized that while the [particulate] traps were ready, the NOx control was not,” Greenbaum said.
Schaeffer of the diesel industry added, “clearly more work is needed on NOx, and 2010 models will deliver that starting January 1, 2010.”
“Everything you do to drive down NOx tends to reduce fuel economy,” he said.
Most diesel manufacturers said they will meet the tougher nitrogen oxides standard next year by equipping engines with new catalysts—a technology called selective catalytic reduction, already used in Europe--and an advanced gas recirculation system.
However, one company, Navistar, has said it cannot meet the standard next year so it will use credits to offset the difference and filed suit against the EPA to change the rule. The other three companies have filed a brief in court supporting the EPA rules.
Other diesels, such as construction and farm equipment, must meet the same emission standards, but have until 2013, or in some cases, 2015, to do so. The new tests only checked truck and bus engines.
To meet health standards at many U.S. cities with heavy particulate pollution, manufacturers of both gasoline and diesel engines may have to face even tougher emission standards in the future, Greenbaum said.
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.
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4 Comments
Add CommentDiesel will be 'clean' when it produces no CO2!
Reply | Report Abuse | Link to thisWhile diesels still emit CO2, they are much more efficient than gasoline. Look at europe, look at Le Mans, look at the ft-lb/gallon comparisons, look at the milage, jump in a VW, & you'll see how much better they are than gasoline engines. Put a turbo on it & add a hybrid system to it, like many manufacturors (Ford, Volvo, VW group, Honda, etc) are doing, & we'll be at least going in the right direction: 60+mpg highway and 50+ mpg city. Plug-ins are worse because of where most electricity comes from: coal. Hydrogen cars have promise but have a while to go. Turbodiesel/hybrids are the way to go in this era.
Reply | Report Abuse | Link to thisI live and drive in Europe on a very regular basis. My own observations of the newer diesels are that:
Reply | Report Abuse | Link to thisi) they regularly produce substantial visible pollution when accelerating.
ii) you can quite clearly smell them from the pavement even if nothing's visible (so there is obviously substantive invisible by products being emitted as well).
This is one report with new engines in a good state of tune.
In human health terms I remain unconvinced that the push for diesel might not eventually be seen as a 21st century equivalent to the decision to put lead in petrol in the last one.
Hydrogen cars may have promise, but hydrogen supply does not. It's not just infrastructure: so far there are only two ways to get hydrogen: by processing fossil fuel (thus producing the same amount of CO2 as burning the fuel directly) or by electrolysis of water, in which case it would more efficient to stuff the same amount of power into a battery.
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