Alternative Fuels Glossary

Alternative fuels have earned plenty of publicity lately. Even so, most unconventional fuel sources and powertrains are in a state of infancy.

Diesel
Essentially fuel oil, diesel has been popular in Europe for decades, but limited mainly to trucks in America. Only Volkswagen and Mercedes-Benz currently offer diesel-powered automobiles.


Modern direct ignition and other control technologies help eliminate the engine knocking and visible exhaust soot that plagued earlier diesel engines.


Diesel is "highly efficient," said Ron Cogan, editor/publisher of Green Car Journal, yielding 30 percent more mileage and 30 percent less greenhouse gases. In California and four northeastern states, diesels don't meet current emissions standards.

"Clean" Diesel
New federal standards for diesel-powered vehicles become effective in 2007. No vehicles meet them now, though Cogan notes that Volkswagen does "expect to meet the standards." By October 2006, cleaner (low-sulphur) diesel fuel is supposed to be on the market.


Ford, among others, is "still working on" a clean diesel, said Paul Kilgore, director of environmental science. Engineers "pretty much know how to deal with particulates," but NOx (nitrous oxides) reduction remains an obstacle.


Kilgore notes two methods to reduce NOx emissions: 1) Precious metal technology, "still in the research stage" and 2) a less-costly method that requires the customer to add an additive every 5,000 to 10,000 miles.

Biodiesel
Domestically produced and renewable, biodiesel can be made from vegetable oils, animal fats, or recycled restaurant greases. Safe and biodegradable, biodiesel reduces such pollutants as particulates, carbon monoxide, hydocarbons, and air toxics.


Some observers have noted that biodiesel vehicles emit an aroma reminiscent of french-fry grease, but that depends on the original source. Biodiesel-powered vehicles "can run seamlessly," Cogan said. "I think biodiesel will be a big thing."

Natural Gas (CNG)
Primarily used in fleets, natural gas is one of the cleanest-burning fuels. It's available through the utility infrastructure.