Environmental Effects of Modern Diesel Fuels and Their Blends

In its 2004 report on sustainable development the previous German government reached the conclusion for fuels that by 2020 the increase in efficiency in diesel and Otto engines as well as innovative power generation concepts will play a central role. Biofuels such as biodiesel will in the future particularly be incorporated as components of blends. The same conclusion was reached by the previous German government for the future use of both Gas to Liquid fuels (GTL) as well as Biomass to Liquid fuels (BTL). Concerning the above formulated theses, the new German government will probably come to a similar assessment, too.

Even if in the report it is assumed that mentionable production capacities for BTL will first be available beginning in the year 2010, for comprehensive use, both biodiesel and BTL blended diesel fuels must be tested in terms of environmental effects from the exhaust gas emissions.

In a network project of the Institute for Technology and Biosystems Engineering of the German Federal Agricultural Research Centre (FAL) in cooperation with the Steinbeis Transfer Center for Biofuels and Environmental Measurement Technology in Coburg and the Center for Occupational and Social Medicine at the University of Göttingen the environmental impacts of different diesel fuels were examined. The research project was sponsored by the Union for the Promotion of Oil and Protein Plants (UFOP) and Shell Research Limited. Now, the project partners presented the final report.

The goal of the project was to make comparative exhaust studies using

  • Shell Middle Distillate (GTL) with lubrication additives
  • fossil diesel fuel (DF)
  • rapeseed oil methyl ester (RME)
  • premium diesel fuel (PDF – comprised of 60% DF, 20% RME and 20% GTL)
  • a blend of 95 % GTL and 5% RME (B5GTL)

In the latter, RME is used as an additive to improve the lubricity. For the studies, a truck engine OM 906 LA from Mercedes-Benz (Euro 3) was used in the ESC test with the mentioned fuel types. The limited exhaust gas components, the particle size distribution as well as the mutagenicity of organically soluble particle fractions were determined.

Overall the GTL fuel consistently produced lower emissions as regular DF, while the particularly low nitrogen oxide emission and the significantly lower mutagenicity are to be emphasized. RME showed advantages in the hydrocarbon, carbon monoxide and particle mass emissions. The premium diesel fuel joins these advantages but causes – like rapeseed oil methyl ester – high emissions of ultra fine particles. While in almost all values, B5GTL showed the expected combination of GTL with little shifting to RME; in the case of premium diesel fuel non-linear effects are seen. These include a lower particle mass emission.

In summary, the project served to study the use of fuels with perceptible biogenic content as well as the effects of GTL (pure and in mixtures) on the emissions. In this sense, it can be called a fuel system technical research approach. In addition, GTL is a prototype for future BTL.

The preliminary test series were conducted on a Euro 3 truck engine without exhaust gas after-treatment. Particularly the non-linear emissions and impact changes show that the studies must be extended to Euro 4 vehicles with exhaust gas after-treatment in order to identify the advantages and dangers of random mixtures of fuels, to recognize the interactions, and to pass them on the engine developers. The project is also the start of the future formulation of an engine and environmentally tolerable biofuel that lies in between neat BTL and neat RME. It shows the potential of fuel research and encourages continuing along the path already started.

The final report of the project with the title “Comparison of Shell Middle Distillate, Premium Diesel Fuel and Fossil Diesel Fuel with Rapeseed Oil Methyl Ester” can be obtained from the UFOP at the english section .

Prof. Dr.-Ing. Axel Munack
Institute for Technology and Biosystems Engineering
Federal Agricultural Research Centre
Bundesallee 50
38116 Braunschweig
Phone: +49-531-596-4201
E-Mail: axel.munack@fal.de