What are the biggest challenges when recycling materials from an old car? Why can't they be used directly in new cars?

Urs Peuker: We build high-quality cars in Germany and use very high-quality materials with a precisely defined requirements profile. When recycling, it must be possible to produce precisely these high-quality materials again. The challenge is therefore the purity of the materials - in the case of metals, the recovery of the alloying elements, for example the copper in steel or the silicon in aluminium. This means that we not only have to optimally separate steel from the rest of the shredded car, but also differentiate between different types of steel. Both are technically complex and require our research efforts.

In addition, the question of whether it is really beneficial to remove individual components from the car before shredding and then process them separately has not yet been fully clarified. This approach is advocated in the new EU Directive, which forms the basis for the German End-of-Life Vehicle Ordinance.

While 50 to 80 percent of steel, copper and aluminium can already be recycled for use in new automotive applications thanks to good recyclability and optimal sorting in the research project, the reuse of automotive glass and plastic is still lagging behind. Why is that?

Sindy Fuhrmann: Glass is more difficult to recover from old cars than steel, as it is often coloured differently, largely coated and combined with other materials. According to the current state of technology, these mixtures are not suitable for closed-loop recycling, i.e. removal from a car for remelting into panes for a new car.

Urs Peuker: The technological challenge is even greater for plastics, as they are damaged by temperature effects or solar radiation during the utilisation phase of the car. Even if we sort plastics very, very well, that doesn't mean that a recycled material designed from them is as good as a new polymer.

Thilo Kreschel: With steel, on the other hand, we were able to recycle 80 per cent of the mass from the end-of-life vehicle in the research project for the industrial production of flat steel for automotive applications.

Let's talk about the subject of glass again: Recycling the glass itself is not a problem? Many people are familiar with a functioning system for the disposal and recycling of bottles and jars...

Sindy Fuhrmann: Correct, on the one hand, the disposal and colour separation of used glass works and, on the other hand, glass fragments from the bottle container are generally not coated and can be melted down easily. Finally, the requirements for bottle glass are lower than for car glass, which is a safety-relevant component. In the case of cars, the glass panes have to be removed and separated from other components, such as rubbers, brackets and films, before the end-of-life vehicle is shredded - usually manually. The so-called crumb glass, i.e. the small pieces of glass, can then be collected and separated or sorted by colour. This is the only way to produce a re-meltable product. In the Car2Car research project, we analysed the different cullet mixtures obtained in detail, melted glass and examined the recycled glass closely under a microscope. This allowed us to deduce how the glass panes from old cars can be handled in order to produce new panes for new cars.

And how do the used metals get back into a new car?

Thilo Kreschel: This is a multi-stage process. At the end of a car's service life, legislation initially stipulates mandatory dismantling scopes for environmental protection and safety reasons, for example operating fluids, batteries, wheels and airbags. The remaining car bodies are then typically shredded in shredder plants. Multi-stage sorting processes are then used to separate the individual materials with the aim of recycling them in the automotive industry. In the case of steel, for example, a large proportion of the steel originally used in a car can be separated from other materials after shredding by means of magnetic separation and further sorting steps.

Urs Peuker: We have also investigated two further sorting steps: Manual separation by human employees and automatic sorting, in which sensors take over the task of material recognition.

Thilo Kreschel: In the project, we were able to prove with our partners, compared to previous practice, that it is possible to produce flat steel for cars using scrap from end-of-life vehicles. Depending on the different process routes in the steelworks and the steel grade, scrap from end-of-life vehicles could be added in quantities of 6 to 50 per cent of the total melt mass - in each case without impairing the steel properties. The rolled and subsequently galvanised material was used to produce over 100,000 series parts at the BMW plant in Leipzig.

What new approaches did you investigate for the recycling of plastics?

Urs Peuker: The focus was on the application of sensor-based sorting processes for real plastic mixtures, which consist of a large number of different materials, some of which are still bonded together. It was found that only small proportions of the plastics are recovered in such a pure state that reuse can be considered. Further research efforts will be necessary, particularly in the pre-treatment of plastics, in order to increase the yield in an expanded technology environment.

What is stopping the automotive industry from putting these findings into practice even more?

Urs Peuker: It is not necessarily the automotive industry alone that is needed to get the materials back into the car. Recyclers, material manufacturers and suppliers are all involved in recycling. The key step for reuse is material purity and therefore material quality. Technology transfer and investment in new and improved sorting techniques are therefore extremely important so that suitable secondary raw materials can be produced in the first place.

Thilo Kreschel: In future, recycling-orientated design and material selection will have to play an even greater role, and not just in the automotive industry. This is the only way to achieve higher material recovery rates and at the same time secure strategically important materials for reuse!

Sindy Fuhrmann: The implementation of glass recycling for the automotive industry is still in its infancy. However, we are already certain that the potential for new recycling chains is huge: by increasing the use of used glass by 10 per cent, the industry could save around 3 per cent energy and therefore CO₂ compared to the current production of new glass panes - and take a significant step towards achieving climate targets through glass recycling.

So can research in collaboration with industry really help to overcome the hurdles of transformation?

Urs Peuker: The Car2Car project shows exactly that: the challenges of all partners along the recycling process were addressed. The open discussion between science and industry makes it possible to conduct solution-orientated research and develop new technologies that can also be scaled up.

Sindy Fuhrmann: Last but not least, I think that the findings from research can be used to develop profitable business models for recycling projects - in the automotive sector and other industries that are in the midst of transformation!