Emission Performance of Selected Biodiesel Fuels

Because of the great interest in biodiesel fuels around the world, the International Energy Agency's Committee on Advanced Motor Fuels sponsored this project to determine emissions and performance of a number of biodiesel fuels with a special emphasis on unregulated emissions. Oak Ridge National Laboratory (ORNL) and Technical Research Centre in Finland (VTT) carried out the project with complementary work plans. Several different engines were used between the two sites, and in some cases emissions control catalysts were used, both at ORNL and at VTT. ORNL concentrated on light and medium duty engines, while VTT emphasized a heavy-duty engine and also used a light duty car as a test bed. Common fuels between the two sites for these tests were rape methyl ester in 30% blend and neat, soy methyl ester in 30% blend and neat, used vegetable oil methyl ester (UVOME) in 30% blend, and the Swedish environmental class 1 reformulated diesel (RFD). ORNL used ASTM 2D diesel as baseline, while VTT used EN 590 (European diesel) as the base. VTT also tested a blend of 30% UVOME with RFD. Steady state test cycles were used for all engines and fuels except for the light duty vehicle, which was tested on a chassis dynamometer using the US FTP 75 test. Results are presented for regulated emissions as well as for aldehydes and composition of particulate matter, and polyaromatic hydrocarbons. VTT also produced results of Ames tests on the mutagenicty of samples of particulate matter. Generally, the biodiesel fuels had higher NO_x emissions but lower values of HC, CO, and particulates. Unregulated emissions varied greatly between fuels and engines.