Myths & Realities: Diesel/Biodiesel

1. All vehicles with diesel engines spew a dark black trail of noxious fumes.

Many Americans have not shed the mental image of diesel cars as an environmental nightmare. This partly explains why diesel vehicles account for only about one percent of new car sales in the United States. It's interesting to note that diesel vehicles in Europe-where by most accounts everything is greener-now account for nearly half of all new vehicle sales. The reality about diesel lies somewhere between Americans' reluctance and Europeans' nonchalant attitude about diesel emissions.

When it comes to greenhouse gas emissions, diesels get high marks. There is a one-to-one relationship between greenhouse gas emissions and fuel efficiency. Because diesels are more efficient than conventional cars, they generate less carbon dioxide (the primary culprit for climate change.) However, diesels emit larger amounts of two other pollutants:

• Particulate Matter: Diesel particulates are harmful to human health as well as aesthetically unpleasing.
• Oxides of Nitrogen : While less visible, NOx is a key ingredient in the formation of urban smog, and also can contribute to the formation of acid rain.

Are these pollutants a big deal? According to the California Air Resources Board, they are. Currently no new diesel passenger vehicles can be sold in the five states that adhere to the more stringent California requirements: California, Massachusetts, Maine, New York and Vermont. The current diesel Liberty, Beetle, Golf and Jetta, in other words, are 45-state vehicles. For 2007 models, only one 50-state diesel car is on the horizon--the new Mercedes E320 BLUETEC to be introduced in late 2006. The 2007 E320 BLUETEC has NOx emissions that are more than eight times lower than the outgoing 2006 E320 CDI.

2. It's hard to find diesel fuel.

Finding fuel for diesel vehicle doesn't require desperate excursions to the truck stop on the edge of town. It only requires a little careful attention to which of your neighborhood filling stations offers diesel. Nearly half of the 180,000 gas stations in the United States serve up diesel to their customers.

3. Using biodiesel in a diesel engine requires a special conversion.

Biodiesel should not be confused with straight vegetable oil, which is untreated oil that some people use as fuel in their modified diesel cars. Biodiesel--a renewable fuel derived from plant oils or animal fats--is a more standardized product that can be used in most diesel engines without any modifications. (Like conventional diesel fuel, biodiesel can only be used in diesel engines.)

Biodiesel can be used in its pure form, which is called B100 (100 percent biodiesel), or can be blended in any proportion with conventional diesel fuel. Common blends include B20 (20 percent biodiesel and 80 percent conventional diesel), and B5 (5 percent biodiesel and 95 percent conventional diesel). According to the Department of Energy, 431 fueling stations in the United States offer commercial biodiesel, although many of these locations sell only low-level blends.

The inconvenience may not be such a big issue--if you're comfortable with switching back and forth from petroleum diesel and biodiesel, or if you're willing to take a do-it-yourself approach. Unlike any other fuel for modern engines, biodiesel can be made at home without investing heavily in special equipment or earning a degree in chemistry. Is biodiesel worth the inconvenience or the extra work? That depends how strongly you feel about using a renewable fuel that can be produced domestically.