Eight Fraunhofer Institutes have developed new solutions for waste management and the circular economy of plastics within the flagship project "Waste4Future ." Leveraging their expertise, they are improving aspects such as recycling, sorting, formulation development, recovery pathways, and the minimization of waste streams. This makes it possible, in particular, to utilize plastic-containing waste that was previously incinerated. The results were recently presented to industry representatives at a final meeting.
High-performance plastics are among the world's most important materials, enabling many applications that offer significant advantages for industrial use as well as for our everyday lives. However, they are mostly produced from fossil raw materials, which entails corresponding CO2 emissions . Furthermore, in Germany alone, more than 6 million tons of plastic waste are generated annually, roughly half of which is currently incinerated rather than recycled.
“The approach of viewing and further utilizing the carbon contained in plastics as a resource is therefore compelling. A prerequisite for establishing such a circular economy is to better identify and utilize carbon-containing components in waste and to transform them into high-quality raw materials for industry. With our combined expertise, we have developed individual and innovative solutions for very diverse waste streams within the flagship project,” says Prof. Dr. Erica Lilleodden, overall project manager of “Waste4Future” and head of the Fraunhofer Institute for Microstructure of Materials and Systems IMWS, which led the project. The Fraunhofer experts focused particularly on the utilization of plastic waste that cannot currently be recycled. To this end, they defined six research priorities: assessment model, sensor technology, sorting technology, material recycling, chemical recycling, and formulation development.
To demonstrate the new possibilities, they produced a chair shell made of recycled polyamide. The plastic was automatically sorted from a waste stream, then processed and injection-molded. The component's performance was compared with virgin material and other available recyclates. The result: The recycled seat shell is competitive in all important aspects. "We focused on polyamide because there is particularly high demand for it from the automotive industry, and demand will increase in the coming years due to strict regulations," says Prof. Dr. Maik Feldmann, Technical Project Manager of "Waste4Future." "With the demonstrator, we in the consortium were able to trace the entire path from the complex waste stream from a shredder light fraction to high-quality recyclates to the new product, and demonstrate how many areas we have made progress in together."
Of particular note is the development of the foundations for a holistic model that allows for the (real-time) evaluation of (plastics) recycling processes according to ecological and economic criteria. The model enables conclusions about the quality of a waste stream and how its individual components can be further recycled with the highest possible value. "By creating digital twins of processes and materials, we have created a way to interact between the real and virtual worlds," says Dr. Gert Homm, head of the "Entropy-Based Evaluation Model" subproject. A sorting demonstrator (a multi-sensor system with AI-based data analysis) was also developed, and the fundamental suitability of THz sensor technology for the previously almost impossible sorting of black plastics was demonstrated. However, this technology still needs to be further developed for the sorting of real waste fractions.
Significant progress has been made in the evaluation of recyclates (e.g., aging processes) and in formulation development (e.g., additives). For example, online rheology was developed as a rapid diagnostic tool for formulation development, such as the use of process stabilizers in polyolefins and coupler additives to increase the molecular weight in polyamides. For polyolefins, the project team identified so-called tipping points as a sorting criterion for cascaded processing. Solvent-based recycling successfully implemented the production of high-purity plastic recyclates. Suitable recycling pathways for polypropylene (PP), polystyrene (PS), acrylonitrile-butadiene-styrene copolymers (ABS), and polyamide (PA) from shredder waste were designed, and mass balances of highly inhomogeneous waste streams (post-industrial and post-consumer plastic waste) were also created.
For chemical recycling (pyrolysis, gasification), the novel entropy model enables a holistic assessment of plastic-containing waste streams. "We were able to demonstrate that gasification and pyrolysis can also be used to recycle polyamide-containing fractions that are no longer mechanically recyclable," says Dr. Jörg Kleeberg, head of the "Chemical Recycling" subproject. The results form the basis for an ASPEN model, which can also be used as a foundation for the synthesis of entirely new plastics.
In all activities, the project partners kept in mind that innovative solutions must not only function in the laboratory, but also be scalable to meet industrial needs. Accordingly, the participating institutes utilized their first-class technical equipment to work in many areas up to the demonstrator and pilot scale. Dr. Elke Metzsch-Zilligen, head of the "Materials Recycling" subproject, concludes: "We always considered the entire system, including the economic evaluation and regulatory framework. The optimizations achieved in sorting, purification, processing of high-quality recycled plastics, and identifying suitable recycling paths offer very attractive new opportunities for waste management and the chemical industry, for example, and even lead to the development of entirely new business models."
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