Audi leads the way in glass recycling

Glass, one of the oldest materials in the world, can be reused almost indefinitely, at least if the containers that are no longer used are deposited in the recycling containers. The used glass collected there returns to a cycle and begins a new life. This should also be possible with automotive glass, thought the experts at Audi, and launched the "GlassLoop" project with the aim of introducing a closed material cycle for automotive glass. Up to now, discarded car windows have been processed into bottles or insulation material, for example.

Three years ago, the team led by Philipp Eder, project manager for circular economy in the supply chain at Audi, began the project of processing discarded windshields so that they could be proportionately reused as windshields in production. The initial step was to find partners who were willing to take on the task. "The unanimous opinion in the industry was that it was not possible to refurbish defective car windshields that could no longer be repaired, because this would lead to production losses due to the high quality requirements for this safety-relevant component," Eder looks back. "By the time we found partners in Saint Gobain Sekurit and the recycling specialist Reiling, the first six months of the project had already passed."

After a subsequent one-year test operation, the processed cullet proved to be suitable for series production, and in the meantime the light has turned green. Since September 1, up to 30 percent of cullet from broken car windshields has been used in the production of windshields for the entire Q4-e-Tron series.

In order for the broken auto glass to be used as a recyclable material for series production, the windshields must first be shredded and then all foreign materials such as wires, adhesives and coatings must be removed. "Even a small stone, for example, can render the glass granulate unusable," explains Eder. The glass is delivered to Saint Gobain by recycling expert Reiling for further processing. "The age of the defective panes is usually irrelevant," explains Eder. However, bottles that end up in the glass container are not usable for the production of car windows, because "they are hollow glass that is not suitable for the demanding production of flat glass. Conversely, however, bottles can be made from car glass. We at Audi want to avoid this downcycling, which is still widespread, in the future. In the future, we want to ensure that a high-quality windshield is proportionately recycled back into a windshield. Before our project, this did not yet exist for automotive flat glass," the project manager continues.

During the one-year pilot phase, Audi experts and partner companies investigated how high the proportion of recycled glass in windshields could be. "In the process, we arrived at a proportion of around 30 percent at which the process can be safeguarded over its lifetime. We have now adopted this value for series production," Eder sums up. The production of the windshield, which weighs around 14 kilograms, thus requires a good four kilograms of recycled glass from automotive glass that can no longer be repaired. Currently, there are considerations to implement other components and models in a further step as part of the circular economy strategy. "If we process car windshields that can no longer be repaired in such a way that they are suitable for automotive production again," says Eder, "we also use fewer raw materials overall, such as quartz sand, at the same time."

In addition to glass, Audi has plans to return other materials such as steel, aluminum, plastics and batteries to automotive production. In another project, the company is working with 15 partners from research, the recycling sector and the supplier industry to investigate the possibilities of reusing these materials from end-of-life vehicles in new vehicles in the Material Loop project. "In the project, we are focusing on cycles within our industry in order to be able to use our products and the materials that have been processed in them for as long as possible," explains Johanna Klewitz, Head of Sustainability in the Supply Chain at Audi.

The findings from Material Loop or Glass Loop also flow into product development at Audi. After all, a circular economy must be thought of holistically: From product design and purchasing, through manufacturing and marketing, to reuse. In the future, the circular economy will therefore play an even more important role in the development of new models. In this context, materials should be selected from the outset in such a way that they can be separated by type at the end in order to be reused in production. (cen/ww)