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Durch das permanente Wachstum der Weltbevölkerung wird der Bedarf von Textilien stetig steigen. Die Produktvielfalt sowie der Konsum der Textilien werden immer größer. Die aktuellen Recyclingtechniken ermöglichen es nicht, den Rohstoffkreislauf für Textilien zu schließen. Dies liegt auch darin begründet, dass derzeit große Mengen der Textilien aus Mischgeweben zwischen Baumwolle und PET bestehen. Die Trennung dieser Komponenten ist jedoch eine Grundvoraussetzung für die Entwicklung eines geschlossenen Rohstoffkreislaufs und stellt gleichzeitig eine große Herausforderung für das Recycling dar. Durch chemische Recyclingverfahren können die Rohstoffe getrennt, aufbereitet und in die Textilproduktion zurückgeführt werden. In dieser Arbeit wird aufgezeigt, wie ein chemischer Recyclingprozess, der einen geschlossenen Rohstoffkreislauf erlaubt, technisch realisiert werden kann. Der Prozess erzeugt eine PET-Fraktion und eine Celluloselösung, die in weiteren Verarbeitungsschritten zu einer Regeneratfaser versponnen wird. In dieser frühen Projektphase werden in dieser Arbeit ebenfalls die Investitionsausgaben und die Herstellungskosten für das Verfahren abgeschätzt.
Circular economy (CE) has received considerable interest in recent years as a strategy to resolve some of our modern urban resource challenges, and circular city models often incorporate systems of urban agriculture in their design. Much work has analyzed the benefits of urban agriculture for creating a resilient food system and as a strategy for supporting urban green space and social cohesion, however, the contributions from business models that operate within urban agriculture have not been thoroughly studied. Many urban agriculture businesses often claim high levels of resource recycling and material circularity, though whether a resource efficiency throughout the entire product lifetime (including energy and material footprint for the cultivation equipment) in comparison to current industrial strategies is truly feasible or even possible is still to be debated. This thesis builds upon work that incorporates social dimensions of CE definitions and begins to research whether the potential resource efficiency contradiction can be justified as to make urban agriculture a valid approach for circular city design. This study examined an urban mushroom farm that implements a circular business model. A qualitative summary of the business operations and resource flows were unpacked and sorted into 24 socio-economic contributions based on their interpreted relevance. The interpreted data shows that an urban agriculture business model can contribute to the building blocks of a CE through economic, ecological, social, and spatial contributions. While these contributions can contribute positively to the operationalization of CE, potential trade-offs regarding resource efficiency, use of urban space, and investment priorities need to be considered and addressed to avoid a possible watering down or greenwashing of the CE concept.
Ground tire rubber (GTR) is a product obtained by grinding worn tire treads before retreading them or via the cryogenic or ambient temperature milling of end-of-life tires (ELTs). The aim of this study is to evaluate if calcium carbonate can be substituted by GTR and, if so, to what extent. Different types of ground tire rubber are incorporated in an EPDM (ethylene–propylene–diene–rubber) model compound as partial or complete substitutes of calcium carbonate. The raw compounds and the vulcanizates are characterized to identify the limits. In general, it is apparent that increasing amounts of GTR and larger particles degrade the mechanical properties. The GTR also influences the vulcanization kinetics by reducing the scorch time up to 50% and vulcanization time up to nearly 80%. This is significant for production processes. The compounds with one-third substitution with the smaller-particle-size GTR show mostly similar or even better properties than the reference.