Strategic network design for recycling of EPS insulation material – insights from a German case study

ABSTRACT

The extensive use of external thermal insulation composite systems (ETICS) using expanded polystyrene (EPS) for building insulation in Germany has resulted in accumulating end-of-life EPS-ETICS. To address limited waste management options and enhance EPS circularity, alternative recycling options like pyrolysis or solvent-based recycling need to be implemented. However, efficient recycling requires ex-ante analyses of the corresponding reverse logistics networks, including all necessary pre-treatment and transport processes. This study aims to develop a decision support system to determine optimal EPS-ETICS waste management by minimising the net present value of the corresponding network design. Our mixed-integer linear optimisation model considers decisions on technology, capacity, and location for pre-processing and recycling facilities as well as on material flow allocation. Applied to a German case study, our model finds pyrolysis and solvent-based recycling economically superior to current waste treatment in waste incineration plants. We present an optimal network design combining central pyrolysis with decentral pre-processing. A scenario analysis shows fluctuating styrene and polystyrene prices might favour solvent-based recycling over the optimal choice in pyrolysis, with minor overall cost differences. Further, legal recycling quotas of at least 40% would be necessary to promote solvent-based recycling and enhance EPS circularity beyond what is achievable through pyrolysis.

KEYWORDS:

• Expanded polystyrene
• ETICS
• chemical recycling
• circular economy
• reverse logistics
• strategic network design

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the Ministerium für Wirtschaft, Innovation, Digitalisierung und Energie des Landes Nordrhein-Westfalen [grant number EFO-001D].

Notes on contributors

Julia Schleier

Julia Schleier studied business administration at the RWTH Aachen University and graduated with a master's degree in 2018. Afterwards, she started her Ph.D. at RWTH Aachen University under the supervision of Prof. Grit Walther on strategic planning and evaluation of reverse logistics systems to close plastic material loops. Her primary research interest revolves around optimising supply chains with a particular emphasis on waste management, reverse logistics, circular economy for plastics, and sustainable development.

Grit Walther

Grit Walther is a full professor and head of the chair of Operations Management at RWTH Aachen University since 2012. She obtained her Ph.D. and habilitation in business administration from TU Braunschweig. Her main research interests are the design of sustainable supply chains and sustainable mobility systems. She uses methods like material flow analysis, multi-objective optimisation, techno-economic modelling, and multi-criteria evaluation. Besides other positions, she founded and coordinated the working group on “Sustainable Supply Chains” of the Association of European Operational Research Societies (EURO) and led the Section on “Sustainability Management” of the German Academic Association for Business Research.