Author: Fraunhofer UMSICHT (as of January 2020)
The Fraunhofer Institute UMSICHT in Sulzbach-Rosenberg develops technical processes for the production of CO2-neutral, standard-compliant fuels (e.g. gasoline or diesel) from biogenic waste materials, for example, from sewage sludge or biowaste.
Fluid energy sources from fossil sources currently still account for about 98 percent of drive energy in transport and 22 percent of heating energy in Germany. Quite a few mobility applications will continue to rely on liquid fuels with high energy density in the future, including aviation, shipping, and heavy road freight.
Biomass-based fuels represent an important complementary function for these applications. In addition, they can help reduce overall CO2 emissions during the period of the transition to battery electric drives. If the fuels are produced from biogenic waste materials in the process, so that their production does not compete with food production, they are referred to as "advanced synthetic biofuels," i.e., advanced, next-generation synthetic biofuels. In the revised version of the Renewable Energy Directive (RED II), legislators are aiming for a quota of such liquid fuels of 3.5 percent by 2030.
Conventional processes to produce liquid energy sources from biomass often have to contend with limitations in terms of the range of possible feedstocks, compliance with exhaust gas standards, and overall energy efficiency. The quality of the products obtained has also been unsatisfactory. In view of this, the Fraunhofer Institute UMSICHT in Sulzbach-Rosenberg has developed a new process for the utilization of biomass residues: the TCR process, it stands for Thermo Catalytic Reforming. In the TCR process, residual biomass is converted into synthesis gas, coal, and liquid synthetic "crude oil", which forms the feedstock for synthetic fuels.
The biomass is gently decomposed into biochar and volatile components in a screw reactor in the absence of oxygen at medium temperatures (< 500 °Celsius). The formation of tar and other pollutants is avoided by optimized process conditions in the various reactor zones. In a downstream post-reformer, the coal and vapors are catalytically upgraded at temperatures of up to 700 °Celsius to improve product quality. The vapors are then cooled. During condensation, oil and process water are separated. The remaining gas is purified.
The result is three products:
The energy required for the process is generated from the residual materials used, so there are hardly any CO2 emissions in the process itself. By definition, the feedstocks themselves also have no "CO2 backpack," as they are residual and waste materials.
The coal can be incorporated into soils, provided the feedstock is not contaminated with pollutants. The carbon contained in the coal is then permanently removed from the atmosphere. (Coal from the TCR process is stable due to low oxygen and hydrogen levels and does not decompose in the soil.) If the carbon is sequestered in this way, the products, i.e. the oil and the gas, acquire a negative CO2 balance, and the fuels become climate-neutral.
Fuels from the TCR process meet the specifications of EN590 (diesel) or EN228 (gasoline) in terms of their chemical composition, according to independent laboratory analyses. The quality has been tested by precise emission and performance measurements on engine test benches and confirmed by several automotive manufacturers. The fuel can therefore be used in vehicles without any further engine modifications. In contrast to alternatives such as ethanol or biodiesel, the fuel from the TCR process can be blended with fossil fuel without limit; there is no "blend limit" here. It can furthermore be marketed as a drop-in fuel, heating oil additive or appliance gasoline.
According to economic feasibility calculations by Fraunhofer, TCR fuel could be produced economically under current boundary conditions. Further cost reduction would be possible by upscaling the technology. The price of TCR fuel would be slightly above ethanol and biodiesel, but still well below the cost of other high-quality alternative fuels, for example, from power-to-X processes.
The current generation of TCR technology plants at the Fraunhofer Institute in Sulzbach-Rosenberg can process 300kg / hour of feedstock and thus produce about 30 liters of fuel per hour. The next large-scale demonstration plant is under construction. (cf. To-Syn-Fuel project)