reFuels are renewable fuels that can be produced in different ways. If these are mixed and processed in such a way that they meet the existing fuel standards, all internal combustion engine applications can be served. This is the result of current vehicle and fleet tests in the “reFuels - Rethinking Fuels” project at the Karlsruhe Institute of Technology (KIT). Compared to purely fossil fuels, the reFuels fuel mixtures enable at least a 25 percent reduction in CO 2 . They also offer slight advantages in terms of pollutant emissions.
"Liquid fuels will be required in the mobility mix for even longer, for example in the field of long-haul heavy goods traffic, shipping and aviation, but also in the existing fleet of cars. , says Dr. Uwe Wagner from the Institute for Piston Machines (IFKM) at KIT. “To do this, it must be possible to generate them sustainably and be available as quickly as possible,” says Professor Nicolaus Dahmen, who is responsible for the supply of fuels in the reFuels project. For all types of fuels commonly used today, there are established and new processes that deliver the respective fuel. “The currently tested reFuels fuel mixtures already enable at least 25 percent CO 2-Reduction compared to purely fossil fuels, ”says Dahmen. In the reFuels project, this could be shown for some examples for which KIT operates technologies or - as in the case of Hydrotreated Vegetable Oil (HVO) - has found another source for the fuels.
Practical tests show positive results
“The reFuels fuel mixtures we have examined so far comply with existing fuel standards for gasoline and diesel fuels. In application tests in cars in the existing fleet, we did not find any negative properties at reFuels. In individual cases, there were even slight advantages in terms of pollutant emissions - both for diesel and gasoline vehicles, ”says Wagner, summarizing the results of the RDE trips (Real Driving Emissions) with commercially available R33 and G40 synthesized at KIT. During RDE trips in Karlsruhe and the surrounding area, he and his team at IFKM examined how reFuels behave in real driving. These trips took place on sections of road in the city, on country roads and on the motorway comply with the current legal requirements for the certification of new vehicles. For the test drives of the KIT, four different cars were equipped with a portable emission measurement device (Portable Emission Measurement System, PEMS). With this device, which is also used in the European research project MetroPEMS, nitrogen oxide, particle and CO2 emissions can be measured while driving. In addition, fleet tests were carried out with six trucks. They covered more than 350,000 kilometers with CARE Diesel® fuel made from 100 percent commercially available HVO. "Here, too, the results did not show any problems in use," says Wagner. An expansion of the fleet and an extension of the endurance run until 2024 are planned for further tests. "Tests on a rail engine with R33 and pure HVO also showed the same results as the road tests," says the expert.
Environmental accounting shows potential benefits
As part of the holistic project concept, the regenerative fuels were subjected to an environmental balance. For this purpose, all essential energy and material flows in connection with the supply and use chain of reFuels and their fossil counterparts were recorded and evaluated. "The results show that the reFuels have significant CO₂ savings potential," says Dr. Andreas Patyk from the Institute for Technology Assessment and Systems Analysis (ITAS) at KIT. “In order to fully exploit the greenhouse gas reduction potential of electrolysis-based eFuels, the electricity must be generated 100 percent from renewable sources.” The CO₂ required for the synthesis can be separated from the air or come from exhaust gas flows from, for example, biogas and sewage treatment plants or cement works.
reFuels are produced at KIT
At the KIT, various fuel mixtures were initially produced from regeneratively synthesized fuel components (reFuels) and fossil fuels using different processes. These fuel blends meet existing standards. The EN590 standard applies to diesel fuels and EN228 to petrol fuels. These fuel mixtures are drop-in capable, which means they can be used in existing internal combustion engines. "But we're not satisfied with that," says Dahmen, "because the goal of the development must be independent fuels without any fossil components."
There are two synthesis plants at KIT for the production of reFuels: In the bioliq® plant on the north campus of KIT, for example, straw is processed to produce synthetic gasoline from second-generation biomass, so-called advanced biofuels. Unlike first-generation biofuels, the synthesis of these advanced fuels from biomass does not compete with the cultivation of food and feed on agricultural land. “We have to avoid the plate-or-tank discussion. That is why we rely on raw materials that are not in conflict, ”says the project coordinator, Dr. Olaf Toedter. In the neighboring Energy Lab 2.0 of the KIT, eFuels are produced from the electrolysis of water with the help of electricity and CO 2 obtained from renewable sources. The main target is kerosene, but diesel and gasoline fractions are also produced. The CO 2 generated when eFuels are burned is compensated for by using CO 2 from the ambient air or from biogenic sources for their production .
The project "reFuels - rethinking fuels"
Since January 2019, the project has been taking a holistic view of the production and use of renewable fuels. Such fuels can drive existing internal combustion engines in the future - in cars, commercial and rail vehicles as well as in aircraft. Six institutes of KIT work together with numerous partners from the energy, mineral oil, automotive and supplier industries under the umbrella of the automotive industry strategy dialogue of the state of Baden-Württemberg on the provision and introduction of reFuels. Two pilot and other pilot plants of the KIT delivered regenerative fuels, which were processed, characterized and tested in test engines. Synthesis processes for reFuels could be optimized in order to reduce raw emissions.