Property Demands on Future Biodiesel
Rapeseed oil methyl ester (RME) is currently not suitable for diesel particulate filters. The boiling characteristic of RME is an additional problem that presumably limits its further usability in Euro VI engines. Currently, hydrogenated vegetable oil (HVO) is in the state of obtaining acceptance as alternative fuel in the German legislation and is in the focus of discussions world-wide. HVO has physical and chemical advantages versus RME. In case RME should continue to be an appropriate fuel its molecule structure must be designed - probably by means of plant breeding. It is important to lower the boiling line by achieving chain lengths between 2and 16 carbon atoms and to have in mind the oxidation stability by focussing the number and the position of double bonds. Moreover, aspects of emissions and health effects must be kept in mind. Besides plant breeding, research should focus on highly efficient biotechnical transesterification, producing simultaneously shorter chain lengths. The phosphorus and metal contents of future biodiesel must become significantly lower than the specification limits that are valid at present.