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Cars that produce no emissions and are equipped with conventional fuel engines could be part of a solution to air pollution. What sounds like an unattainable dream has been scrutinised by scientists at the TU Munich. Instead of diesel or gasoline fuels, they rely on synthetic energy suppliers such as the oxymethylene ether group. In contrast to conventional fuels, artificially generated fuels do not produce any emissions because they burn almost residue-free. This could herald the end of fine dust, carbon dioxide and nitrogen oxide pollution. And above all, improve air quality in the emission-stricken cities.


The project XME-Diesel was launched to find out how synthetic fuel behaves in engines and which adjustments are necessary. It is funded by the Federal Ministry with the aim of advancing the use of OME (oxylmethylene ether). Scientists from the Chair of Internal Combustion Engines at the TU Munich are involved in this project.

Using computer simulations and tests on a test bench for single-cylinder engines, the experts determined the optimum parameters for efficient combustion. Since OME has a lower calorific value than diesel, the engine must be supplied with more fuel. Only then can the same performance be achieved. On the basis of these results, the scientists adapted the injection valves.

A significant advantage of synthetic fuel is that it does not produce soot. In addition, a large proportion of the exhaust gases can be fed back into the engine. This does not contaminate the inlet tract. As a result, hardly any nitrogen oxides are produced, since the recirculated exhaust gases prevent very high temperatures during combustion.

Finally, the scientists tested a test bench for full engines – a series engine with six cylinders. It was converted for operation with synthetic fuels. This confirmed the previous results.

High costs

“We have found that the use of fuel can significantly reduce pollutant emissions,” explains Dr. Martin Härtl, who is coordinating the project. “The Euro 6 level, i.e. the applicable limit value, can be easily achieved with synthetic fuel. We are also convinced that with an efficient exhaust aftertreatment system, emissions can even be reduced to almost zero.” Another interesting aspect is that OME can be obtained from waste CO2. In other words, carbon dioxide, as it is produced during work processes in the steel and cement industries as well as in coal and gas-fired power plants. Together with electricity from renewable sources, the synthetic fuel would even be climate-neutral.

According to the scientist, OME could be of particular interest for vehicles and systems that cannot be converted to electric drives. For example, for energy supply in remote areas or in aviation and shipping.


Photo: Moritz Ermert / TUM