Emissions of carbon monoxide declined by 12 to 14 percent, and hydrocarbons by 10 percent, he added. Biodiesel fuel is made by a reaction of vegetable oils with methanol or ethanol. The result is a less viscous, more volatile fuel. Changing the ignition timing of the engines reduced NOX emissions. The reduction in carbon monoxide emissions is probably due to the higher oxygen content of the biodiesel fuel, the researchers say.
More oxygen means the fuel is burned more completely.
More complete burning also helps reduce hydrocarbon emissions. The researchers attributed the 25 percent reduction in particulate emissions to the lower aromatic and sulfur content of biodiesel fuel, and its greater oxygen content. The biodiesel study at West Virginia University was funded by the United States Department of Energy's Office of Transportation Technologies. A nonprofit organization with a membership of 161,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals and databases, convenes major research conferences, and provides educational, science policy and career programs in chemistry.