Technical Committee Automotive Fuels

Biofuels - Properties and Experiences with their Use

The European Union wants to promote the use of renewable raw materials also in the traffic sector in order to meet the internationally committed reduction of carbon dioxide emissions. At the same time a new market shall be created for farming and jobs shall be secured. Fatty acid methyl esters in the diese! market and ethanol and ethyl tertiary butyl ether (ETBE) in gasoline are discussed as compounds that can be produced from renewable raw materials and be applied as fuels in the short term.
This Iiterature survey deals with the extent of C02 I greenhause gas emission reductions, the availability of biofuels and summarizes the economical and technical experiences obtained so far with their application. The use of pure vegetable oils, dimethylether and pyrolysis oil is also briefly covered.
lf biodiesei (in Germany normally rape seed methyl ester, RME) is used, problems resu!t especially from storage over a iong period of time. Fatty acid methyl esters are prone to oxidation and to contact with water. ln the presence of water they may decompose by hydrolysis and show microbial attack. ln the car industry metals and elastemers have to be used that are compatible with fatty acid methyl esters. ln general there is still a Iack of sufficient experience in everyday use. Therefore the car manufacturers are reluctant to use biodiesei in cars due to its possible technical risks.
Already today ethanol and ethyl tertiary butyl ether, a compound very similar to methyl tertiary butyl ether, are used internationally in limited amounts as fuel components. Therefore the technology is available to modify existing cars so that they become compatible with these oxygenates. With alcohol containing gasolines problems may arise from the formation of a water-alcohol phase. At high alcohol concentrations the engines have to be adapted to the changed combustion parameters.
The emissions of carbon monoxide, hydrocarbons and polycyclic aromatic hydrocarbons decrease if biodiesel, ethanol and ETBE are used, emissions of nitrogen oxides in most cases increase slightly. The volumetric fuel consumption normally increases, if biofuels are used.