Synthetic, CO2-neutral fuels

Fraunhofer enables the production of standard-compliant fuels (diesel or gasoline) from waste materials such as sewage sludge.

© Fraunhofer UMSICHT
Walter Röhrl refuels an Audi R8 with synthetic fuel from sewage sludge
© Fraunhofer UMSICHT
Fuels from the TCR process are 1:1 engine compatible and have no blend limit

Within the framework of various projects, Fraunhofer UMSICHT is developing processes for the production of »synthetic fuels« with the quality of standard fuels from currently available raw and residual material sources.

This research field is based on the fact that combustion engines will continue to make a significant contribution to our mobility despite emissions and increasing electromobility. Although automobile manufacturers have announced specific targets for phasing out combustion technology, it is uncertain to what extent and within what timeframe these targets can be implemented in the market.

CO2 reduction with combustion engines

It also needs to be clarified how the remaining combustion engines will be integrated into a concept for CO2 reduction. Forecasts for 2030 assume that - with a stock of 10 to 13 million electric cars - more than 70 percent of vehicles will still be equipped with combustion engines. In addition, there will be heavy-duty and long-distance traffic as well as aviation and shipping - areas that will be hardly or only partially electrified in the foreseeable future.

Sustainable synthetic fuels with minimal CO2 footprint

In order to achieve a significant reduction in CO2 emissions in the areas mentioned, liquid fuels with a high energy density must be produced sustainably. In the short and medium term, preference should be given to »mature« technologies and existing, sustainable raw materials (e.g. biogenic residual and waste materials).

On the part of the legislator, there is additional pressure to act with regard to the revision of the Renewable Energies Directive (RED II), as a quota of progressive liquid fuels of 3.5 percent is aimed for by 2030. Market-ready, short-term solutions with a relevant impact on GHG emissions can now be realized with biofuels alone.

TCR process: Standard petrol and diesel

© Fraunhofer UMSICHT
TCR pilot plant in Sulzbach-Rosenberg

At Fraunhofer UMSICHT, a standard-compliant fuel is produced from residual materials such as sewage sludge or organic waste using the TCR® process (Thermo-Catalytic Reforming). In »thermo-catalytic reforming« (further information: TCR process) biomass is converted into high-quality product oil and synthesis gas in a multi-stage thermal process. These intermediate products can be further processed, for example in a refinery, to produce fuels that comply with standards.

TCR fuels can replace fossil fuels 1:1

According to independent laboratory analyses, the chemical composition of fuels from the TCR process meets the specifications of EN590 (diesel) and EN228 (petrol). The quality has been tested by precise emission and performance measurements on engine test benches and has been confirmed by several automobile manufacturers. The fuel can therefore be used in vehicles without further engine modifications.

In the measurement of raw engine emissions, the fuel was compared with fossil diesel to analyse the influence on combustion, with unchanged engine operating parameters. It was shown that the performance is similar to that of fossil fuels, with only slight differences in exhaust emissions. For NOx, there is a slight increase; for CO, CH and CO2, an improvement, i.e. a reduction in emissions, can already be seen in the 25% blend used.

In contrast to alternatives such as ethanol or biodiesel, the fuels from the TCR process can be blended with fossil fuels without limit, there is no blend limit here. It can also be marketed as a drop-in fuel, heating oil additive and portable gasoline.

TCR fuels are CO2-neutral

For the TCR® process, GHG emissions were balanced on the basis of the »Method for calculating the greenhouse gas reduction achieved through the use of biofuels on the basis of actual values« (»Ordinance on Requirements for the Sustainable Production of Biofuels« (Biokraft-NachV), § 8 para. 2).

The fuels from the TCR® process as a substitute for fossil fuels can be produced in a CO2-neutral manner when waste is used - in the calculation example for sewage sludge - and the carbon produced by the process in the form of coal is partially sequestered.

Economy of synthetic fuels

According to initial profitability calculations, the fuel (green diesel and green petrol) could be produced at 75 cents per litre (before tax). A further reduction in costs by upscaling the technologies is foreseeable in the future. This means that the price is slightly above the cost of ethanol and biodiesel, but still significantly below the cost of other high-quality alternative fuels, e.g. from PtX processes (2-5 €/l).

TCR technology: Development status

The current generation of TCR technology systems at the Fraunhofer Institute in Sulzbach-Rosenberg can process 300kg / hour of feedstock and thus produce approx. 30 litres of fuel per hour. The next large-scale demonstration plant is currently under construction. (see To-Syn-Fuel project)

Significant research work for the TCR® process was carried out within the framework of the Center for Energy Storage, which was funded by the Bavarian Ministry of Economic Affairs at the Fraunhofer sites in Sulzbach-Rosenberg and Straubing with over €16 million.

Test vehicle »VW XL1«

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1 litre car with hybrid drive: VW XL1

The XL1 lightweight vehicle was developed and built by Volkswagen (VW) in a small series of 250 units between 2014 and 2016. The state-of-the-art diesel engine is characterized by its low fuel consumption and was the decisive criterion for using this limited super-economy car as our test vehicle.