Waste4Future – Sustainability Assessment of Recycling Process Networks
M. Vogelgesang1*, C. Li1, E. Ionescu1

1 Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS
*malte.vogelgesang@iwks.fraunhofer.de


For many waste streams including a large share of plastics, incineration is still the predominant treatment option. However, the current stringent climate situation requires drastic action concerning the emission of fossil carbon into the atmosphere. One effective strategy to minimize the dissipation of fossil carbon is to keep the already extracted fossil carbon within the anthroposphere, e.g., through recycling. Over the past years, a vast variety of physical and chemical recycling processes for plastic waste have been developed, each with specific pros and cons. For highly heterogeneous mixtures, such as automotive shredder residues, different processing options can be beneficial for the various materials in the mix. [1, 2]
In the Fraunhofer Lighthouse Project Waste4Future, various processing options for the plastic waste and its constituting elements have been assessed with regard to different relevant indicators such as recycling rate, energy consumption etc. Thus, new sensors for particle-based sorting are developed and novel applications for mechanical and chemical recycling are put to the test. Moreover, digital twins of the investigated processes are elaborated and used to establish an assessment model to flexibly evaluate the process combinations concerning the parameters mentioned above and to identify the most valuable processing path for waste streams with specific compositions (Figure 1).

   
Figure 1. Information flow between the physical world and the assessment model

Based on experimental data and simulations for material and feedstock recycling, the material flow is automatically modelled for all available process cascades. Subsequently, a sustainability assessment is conducted including global warming potential (life cycle assessment), operating expense and expected revenue (life cycle costing), as well as the changes in entropy for material mixtures and carbon.
Preliminary results clearly indicate the benefits of mechanical over chemical recycling. From a climate perspective, recycling of plastic waste is seen to be preferable even to the status quo of efficient energy recovery as substitute fuel. Currently, the assessment model is being expanded by considering additional plastic waste treatment processes such as regranulating, selective extraction, pyrolysis, gasification as well as incineration. The ultimate aim is to build and validate a flexible dynamic model to automatically identify the most sustainable process cascade for planning, but also for operation of (plastic) waste recycling networks.

References
[1] R. Geyer Science Advances, 2017, volume 3, pages e170078.
[2] I. Vollmer, Angewandte Chemie International Edition, 2020, volume 59, pages 15402-15423.