Biodiesel doesn’t lead to higher emissions of ultra-fine particles

Final Report to the Research Project „Measurement of ultra-fine particles in the exhaust gas of diesel engines fuelled with biodiesel“

Measurements of exhaust gas were carried out for a heavy-duty engine using four different fuels: biodiesel (B100); fossil diesel fuel; Shell V-Power® diesel fuel; and a blend of Aral Ultimate® diesel fuel with 5% biodiesel. The aim of the underlying research project – entitled “Measurement of ultra-fine particles in the exhaust gas of diesel engines fuelled with biodiesel” – was to examine in detail the increase in ultra-fine particles that is observed when biodiesel is used instead of fossil diesel fuel. An assessment of the risks of exposure to ultrafine particles was expected as the outcome of the research.

In parallel, the regulated emissions were determined. For these, a relative advantage was observed for biodiesel – with the exception of higher NOX emissions. When using an oxidation catalytic converter (DOC), the oxidizable components of the exhaust could be diminished, in part drastically. For biodiesel, the examination of the particle mass revealed a relatively high amount of unburned fuel.

After applying a heated dilution system to the exhaust gas before entering the analyzer, a considerable decrease of ultra-fine particles in nuclei mode (with aerodynamical diameters ranging from 10 to 30 nm) was observed. When using a DOC, the nuclei mode particles were clearly diminished, too, and could not be diminished further by heated dilution. This leads to the conclusion that the ultra-fine particles of nuclei mode mainly consist of unburned fuel and not of soot, which would have to be considered as possibly harmful to human health. By optimized sampling it could be shown that biodiesel exhibits the lowest emissions of ultrafine particles, whereas the other fuels, compared to each other, revealed similar particle size distributions.

As a result of the project one can draw the conclusion that biodiesel does not lead to an increased emission of ultra-fine particles.

The project was funded by the Fachagentur Nachwachsende Rohstoffe e.V. (FNR – Agency of Renewable Resources), the Union zur Förderung von Oel- und Proteinpflanzen e.V. (UFOP – Union for the Promotion of Oil and Protein Plants) and the Verband der Deutschen Biokraftstoffindustrie (VDB – Association of the German Biofuels Industry). It was carried out at the Institute for Technology and Biosystems Engineering of the Federal Agricultural Research Center (FAL) in Braunschweig, Germany, in cooperation with the Steinbeis Transfer Center for Biofuels and Environmental Analysis, Coburg, Germany (Prof. Dr. Jürgen Krahl).

The report can be downloaded here.