German automaker Audi is exploring different technologies that will allow more recycling of plastics from end-of-life vehicles.
The work is part of Audi’s efforts to improve its environmental performance. To make it happen, the carmaker is working with partners from science and industry, including Germany’s Fraunhofer Institute.
The pilot study with Fraunhofer involves physical recycling to gain experience with as many technologies as possible to establish material cycles for production. These cycles, Audi executives say, cut two ways: They reduce demand for renewable and raw nonrenewable materials while also identifying materials with a more favorable energy footprint.
Since different types of plastic require different sorting and recycling technologies, Audi is looking at several options at the same time: mechanical, chemical, and physical recycling.
By testing different approaches, optimal sustainable choices can be made. Anything that does not make sense from an ecological point of view will be discontinued after the pilot phase, the company said.
“Our focus is always on getting as many plastic contents as possible out of the car at the end of its life in order to be able to recycle them again,” explained Mike Herbig of Audi’s polymer team.
Some 200 kilograms of plastics and plastic composites are typically used in vehicles today. Bumpers, front grilles, interior parts, and components in the powertrain and air conditioning are made of plastics.
In the automotive industry, stringent quality standards apply regarding the material used, both virgin and recycled. Crash safety, heat resistance and resistance to substances such as organic solvents, oil or hydraulic fluids must all be guaranteed, in addition to factors such as dimensional stability, quality, feel, appearance, and smell that must be maintained throughout the vehicle’s entire service life. Environmental requirements are also increasingly being taken into account.
“We only use a recycled material if the components made from it also meet the requirements, which is to say if the quality of the parts remains the same over their entire useful life,” Herbig said.
Mechanical recycling, while the first processing choice, cannot always deliver the required quality or performance, nor is it a suitable solution for components made from composites or that incorporate various adhesives, coatings, and fillers. Working with the Karlsruhe Institute of Technology (KIT) and industry partners, Audi has already developed a chemical recycling method, where mixed plastic waste is processed into pyrolysis oil that can replace virgin crude as feedstock in the cracker. Components produced from the output of the cracker feature properties similar to those made from virgin material.
Now the new study on physical recycling — which Audi is developing in cooperation with the Fraunhofer Institute for Process Engineering and Packaging IVV — will determine the possibilities of the physical recycling of automotive plastic waste and its reuse in vehicles.
Unlike in the chemical recycling process, where the waste plastic is reduced to its molecular constituents, physical recycling makes use of solvents. No chemical degradation reaction takes place and the polymer chains remain undamaged.
“Only substances that are absolutely harmless are used as solvents,” said Martin Schlummer of Fraunhofer IVV.
Dissolved substances such as flame retardants can also be separated from the plastic solution if necessary. The process yields a very pure plastic granulation that matches the quality of virgin material.
Audi is now piloting the production of larger quantities of this granulate, in order to validate the technical feasibility of the process and to test its cost-effectiveness. The company will produce a small component like a seat adjuster during the pilot — a part that nonetheless must meet high standards in terms of emissions and odor.
In the future, Audi wants to further increase the proportion of recycled materials in vehicles. According to the automaker, the Audi Q4 e-Tron already boasts up to 27 components made with recyclates, including the mounting bracket, a component that has to meet particularly high demands in terms of mechanical properties.
Audi views the different technologies as complementary to one another and in the future, plans to use all three. In this way, it will be possible to establish material cycles for raw materials by taking optimum advantage of the valuable resources contained in end-of-life vehicles.