Using biodiesel in diesel engines helps reduce harmful engine emissions, according John Nowatzki, North Dakota State University Extension Service agricultural machine systems specialist.

""With the increasing availability of biodiesel for both on- and off-road use in diesel engines, there also is increasing interest in the effect of its use on the environment,"" he says.

The U.S. Environmental Protection Agency (EPA) conducted a comprehensive analysis of biodiesel impacts on exhaust emissions in 2002. It found that tailpipe emissions from engines using biodiesel are significantly lower than the emissions from similar engines operated on petroleum diesel. Hydrocarbon emissions from engines operated on B100, (100 percent biodiesel) were about 67 percent less than petroleum diesel fuel emissions. Hydrocarbon emissions from engines contribute to ozone formation and are a key component of smog.

Particulate matter and carbon monoxide emissions from engines using biodiesel were 48 percent less than petroleum diesel. Particulate matter is very fine particles that can remain suspended in the atmosphere and contribute to smog. Carbon monoxide is a poisonous gas that is most dangerous in confined areas.

""The pollutant that is more serious from engines operated on biodiesel, compared with petroleum, is nitrogen oxide,"" Nowatzki says. ""Nitrogen oxide emissions are about 10 percent higher using biodiesel. Reducing nitrogen oxide emissions is a crucial component of EPA's strategy for cleaner air and reducing acid rain. There is an effort to modify diesel engine combustion and exhaust systems to reduce nitrogen oxide emissions."

Emissions of carbon dioxide (CO2), a gas that is increasing in the atmosphere, are similar from engines operated on biodiesel or petroleum diesel. However, the carbon dioxide produced from burning petroleum diesel and emitted to the atmosphere comes from sources long sequestered in the earth. Oil seed crops actually take carbon from the atmosphere during their growth cycles and store that carbon in the ground.

""When comparing the total life cycle of carbon emissions from the two fuels, petroleum diesel has a more negative effect on the environment,"" Nowatzki says. ""A study of the biodiesel and petroleum diesel life cycles jointly found that because biodiesel production requires such small amounts of fossil fuel, its CO2 life cycle emissions are much lower than those of petroleum diesel. Biodiesel reduces net CO2 emissions by more than 78 percent compared with petroleum diesel. A primary conclusion of the study is that displacing petroleum diesel with biodiesel in urban buses is an extremely effective strategy for reducing CO2 emissions."

The study was conducted by the U.S. Department of Agriculture and Department of Energy.

Biodiesel produces no sulfates when burned in diesel engines. Reducing sulfates is another part of the EPA's strategy to for cleaner air. Since there are zero sulfates in biodiesel, its use in diesel engines offers an excellent alternative to even the ultralow sulfur diesel fuels mandated for use in over-the-road diesel-powered vehicles.

More information on using biodiesel in engines is available on the NDSU energy efficiency Web site at http://www.ag.ndsu.nodak.edu/abeng/energy_efficiency/.

NDSU Agriculture Communication