Protecting the climate with fuels from waste - that is the project of researchers at the University of Applied Sciences in Hamburg-Bergedorf. In a pilot plant, they produce bio-crude oil and artificial diesel from used cooking oil. Conventional cars and trucks could easily be refueled with the climate-neutral fuel, says project manager Thomas Willner. The plant needs one kilowatt hour of electricity to produce one liter of fuel. In order to let a car drive 100 kilometers, around 5 kilowatt hours of electricity are needed. An electric car, on the other hand, consumes around 15 kilowatt hours on this route, says Willner's colleague Anika Sievers.
Artificial fuels are not a new idea. The Finnish group Neste already produces hydrogenated vegetable oil in large refineries in Rotterdam, Singapore and in Porvoo, Finland. According to industry estimates, 30 million tons could be produced annually by 2025, says Willner. What is special about his READi-PtL (Reactive Distillation Power to Liquid) project is its efficiency: A plant for the production of several thousand tons of fuel can be set up right next to a disposal facility and work economically.
Old cooking fat from the canteen
In fact, this is already planned. The company Nexxoil wants to build a first production facility in the Hamburg area by the end of the year, and a second one in Bavaria next year, according to Managing Director Thorsten Dunker. Another cooperation partner of the Hamburg university project is the Schleswig-Holstein waste disposal company KBS. It is currently supplying the used grease from which Willner and Sievers produce around two tons of fuel a week.
In the workshop on the Hamburg campus there are several large plastic containers, about one meter high. They contain old cooking fat from the university canteen. It is preheated and thoroughly stirred (homogenized) in a tank of the plant, which is housed in a blue standard container. The liquid fat is pumped into a reactor. The cylinder-like device, about five feet tall, is mounted in a container above.
At a temperature of 350 to 400 degrees, the relatively large hydrocarbon molecules in the fat are "cracked", ie broken up, explains Sievers. Finally, the molecules evaporate and are cooled down again in a condenser. In a first stage, the organic crude oil is produced. In a second stage, raw materials are produced that can be used in the chemical industry. However, the molecules would have to be "designed" beforehand, says Willner. The researchers do this by adding hydrogen.
In addition, gases such as methane, ethane and propane are formed in the reactor, which are to be used in the future to heat the plant. "The process could run independently," says Willner. What remains is a type of charcoal that can be introduced into the earth as a soil conditioner and thus bind CO2 in the long term. In addition, waste water remains, from which biogas can still be obtained. In the future, the Hamburg process engineers want to use plastic waste as a raw material for their climate-neutral oil substitute.
So-called e-fuels can also be produced from synthesis gas in a different way. In this process, carbon dioxide from the air is used to obtain a gas mixture of carbon monoxide and hydrogen for further processing. Researchers at the Karlsruhe Institute of Technology use the so-called Fischer-Tropsch synthesis to produce e-fuels. However, critics complain that the process requires a lot of electricity. But according to Willner, this approach makes sense, for example in countries with a large surplus of solar energy, such as Saudi Arabia.
Critical von Greenpeace
Greenpeace recently accused Federal Transport Minister Volker Wissing of "raising false hopes with their e-fuel fairy tales with fatal consequences for industry and the climate". Sievers, on the other hand, says: "Combustion engines will be around for a long time." The aim is to involve all vehicles in climate protection. The professor is convinced: "We could achieve that directly with the fuel that we produce here."
Hamburg's Science Senator Katharina Fegebank was enthusiastic at the official opening of the plant in February: "Sustainable fuels are an important building block for becoming independent of fossil fuels in the future," said the Green politician.