Biodiesel Vehicle Emissions
When used as a vehicle fuel, biodiesel offers some tailpipe and considerable greenhouse gas (GHG) emissions benefits over conventional gasoline and diesel. The GHG emissions benefits of biodiesel are especially significant, because carbon dioxide (CO2) released during fuel combustion is offset by the CO2 captured by the plants from which biodiesel is produced.
Improved emissions performance of today's high-tech diesel vehicles are the result of the integration of sophisticated engine controls. Fueling and exhaust after treatment devices also determine how clean a vehicle or engine will be.
All 2010 and newer engines and vehicles will have to meet the same emissions standards, regardless of fuel type. So a light-duty diesel vehicle will need to meet the same stringent emissions standards as a gasoline or ethanol-powered vehicle. The same is true for medium- and heavy-duty vehicles; all vehicles meet the same emissions, regardless of whether they use biodiesel or not. Integration of sophisticated engine controls—as well as fueling and exhaust aftertreatment devices—are the determining factors governing how clean a vehicle or engine can be.
Life Cycle Emissions
Life cycle analysis is a technique used to assess the environmental impacts of all stages of a product's life, including raw material extraction, processing, manufacturing, distribution, use, and disposal or recycling. When comparing fuels, a life cycle analysis may focus on particular portions of a fuel's life cycle, such as from extraction-to-use or well-to-wheels, to determine the merits or problems associated with each fuel.
Life cycle analysis completed by the National Renewable Energy Laboratory, and later by Argonne National Laboratory, found that greenhouse gas emissions for 100% biodiesel (B100) could be more than 52% lower than those from petroleum diesel. These analyses also showed that biodiesel may reduce petroleum use by more than 88% throughout its life cycle.