Emissions: The Diesel Age

Diesel fuel and diesel-powered vehicles may find themselves thrust into the limelight in 2007, thanks to the convergence of several simultaneous events:

• In October, new ultra-low sulfur fuel for on-highway vehicles entered the marketplace with relatively little disruption to price or supply. The new fuel will not only reduce emissions in and of itself, but it also allows manufacturers to use new aftertreatment technologies that will achieve additional, dramatic reductions in emissions, particularly the black soot that has tarnished diesel's image.
• In January 2007, the federal government's new regulations for on-highway vehicles took effect, mandating the use of new "clean diesel" engines, the first significant upgrade in on-highway diesel technology since 2002.
• Rising fuel prices and escalating concern over global warming have increased the public's interest in alternatives to gasoline, including diesel the most energy-efficient fuel.

Introducing the public to "clean diesel"

High gas prices and the introduction of new ultra-low sulfur fuel have given the diesel industry a golden opportunity to reintroduce itself to the public. Most people associate diesel with the smell and smoke from old buses and dump trucks. However, as industry spokespersons are quick to point out, that image is no longer valid: The new on-highway engines reduce emissions by 95% and generate virtually no soot.

In addition, they consume much less fuel than their gasoline-powered counterparts because diesel fuel is 30% more energy efficient than gasoline. With rising gas prices prompting many people to look at hybrid vehicles that use a combination of gas and electric power, diesel manufacturers are moving quickly to get people to give diesel a consideration, as well. Volkswagen and DaimlerChrysler have unveiled several new diesel vehicles to compete against gas-electric hybrids and BMW is expected to follow suit. With diesel-powered cars now accounting for just 3% of new car sales in the United States, they hope to replicate the success they've enjoyed in Europe, where about 50% of all new cars sold are diesel-powered.

Diesel engines and global warming

Diesel fuel may also get a boost from the public's concern over global warming. Diesel-fueled engines emit the fewest greenhouse gases believed to promote global warming, particularly carbon dioxide. In fact, the use of regulations and tax incentives to promote the use of diesel-powered vehicles was one of the principal strategies employed by European countries to meet the requirements of the Kyoto Protocol, an international agreement on global warning.

While the United States did not sign the Kyoto Protocol, it has not escaped the debate over carbon dioxide emissions. The U.S. Supreme Court is currently considering whether the Environmental Protection Agency (EPA) has the authority to regulate carbon dioxide emissions from vehicles and equipment.

Environmental groups and state regulators asked the EPA to draft regulations restricting carbon dioxide emissions from vehicles and power plants, but the agency determined the Clean Air Act and its subsequent amendments did not give it that authority. The U.S. Court of Appeals of the District of Columbia upheld the EPA's decision on a 2-1 vote, which was subsequently appealed to the U.S. Supreme Court.

The court's ruling could have a significant impact on the public's perception of diesel as an environmentally friendly fuel. Carbon dioxide emissions are directly proportional to fuel consumption. Because diesel-powered vehicles consume 30% less fuel than their gasoline-powered counterparts, they emit 30% less carbon dioxide. Diesel also stacks up better than natural gas, LPG and other alternative fuels considered environmentally friendly. While these fuels are considered "clean" they are less energy efficient, which means they generate more carbon dioxide to accomplish the same task as a diesel-powered engine.