High-performance plastics are among the world's most important materials and a prerequisite for many applications that provide significant benefits for industrial use and everyday life. However, they are usually made from fossil raw materials, resulting in considerable CO2 emissions. Germany alone produces more than 6 million tons of plastic waste every year; around half of this is still incinerated instead of being recycled.

It therefore makes sense to consider the carbon in plastics as a resource that is to be reused. Prerequisites for this are improved identification and recycling of carbon components in waste and the conversion back into high-quality raw materials for industry.

This is where the Fraunhofer Waste4Future flagship project comes in with a sub-project that made it possible to sort difficult-to-separate black plastics. It uses thermography to precisely distinguish polyamides and polypropylene in black plastic waste. The recycling sensor and data system developed as part of the project thus forms the basis for comprehensive plastic waste recycling, with the researchers using machine learning to analyze large amounts of image data in order to identify the thermal properties in the various plastics, which allows them to characterize these. This innovative process has the potential to drastically reduce carbon loss during recycling.

Sustainability

How does your product contribute to the promotion of sustainable production or industry, particularly in relation to our theme “Energizing a sustainable industry”?

The further development of our sensor system forms the basis for a holistic model and allows plastic recycling processes to be evaluated in real time based on environmental and economic criteria. The model provides information about the quality of a waste stream and how its individual components can be recycled for use in high-quality applications.

Comprehensive recycling of plastic waste without carbon loss is a noteworthy example for a sustainable recycling process and a closed plastic cycle that produces high-quality raw materials. This makes today's waste a green resource of the future and simultaneously reduces industry dependence on imported primary carbon resources such as oil and natural gas.

Future outlook

How do you see the future development of your product, especially with regard to the growing demand for sustainable solutions in industry?

The optimization achieved in sorting, purifying and processing high-quality recycled plastics and the identification of suitable recycling paths offer very attractive new opportunities, including for waste management and the chemical industry. This could even lead to the development of completely new business models. Upcoming strict regulations for the automotive industry in particular will result in an increasing need for sustainable plastics (such as polyamide), which will in turn create a growing demand for these materials.

To demonstrate the new possibilities, the researchers produced a chair shell from recycled polyamide. The plastic was automatically sorted out of a waste stream, then processed and injection molded. A comparison of the performance of these components with virgin material and other available recyclates showed that the recycled seat shell was competitive in all relevant aspects.