## 2 Materials and Methods
### LCA Modelling Approach for a Closed-Loop System  
Based on this information and the respective LCI data provided by all partner companies (for details, see SM), an interlinked product system according to Figure 2 is modeled within the LCA software system. The first jacket produced is the result of the blue highlighted product system. This first product system is unique compared to all following product systems (in orange) because (1) the main ingredients for the fabric are about 650 g of PET bottles entering the system and (2) the auxiliary products include the zipper that has to be produced for this very first loop. All following product systems (in orange) do not include the production process of the zipper, as it is reused from the first jacket (outflow of the previous dismantling process--shown inside the circle in Figure 2). The PES material that is lost along each supply chain is replaced by the following supply chain with virgin PES (orange box on the very left). The reason why virgin PES is used instead of PET bottles is the high-quality requirements of the fabric. If PET bottles or other PES waste streams were used to replace the missing raw material part, the PES granulate would degrade after each recycling loop. Material losses along the supply chains result because of efficiency losses at every process step. The process efficiencies are given in the right upper corner of each box in Figure 2. Where no percentage is given, data were not available or no sound estimate was possible. Note that the membrane, lining and all auxiliary products (except the zipper) must be re-produced again for every product system. During the four years use phase, the jacket is washed three times in an industrial setting. The blue and orange product systems (\"loops\") are closely interconnected. The orange version reuses the zipper and PES material from the blue one. Therefore, in this model, the blue loop is the first product system and the orange one comes second. In theory, there can be an infinite number of product systems connected with each other, as long as the recycled PES material keeps the required quality for producing new fibers again. For this reason, different scenarios are modelled in the results section to test how a varying number of connected product loops alter the environmental impact compared to the linear product system. Three scenarios are modelled in this study. Each scenario assumes a different number of orange loops connected to one blue loop. In the first scenario, three loops (one blue and two orange ones) are modelled. The second scenario  
Figure 2: Multiple wear2 wearTM product systems interlinked by recycling and reusing activities (in blue the first loop—in orange all subsequent loops). The raw material (polyethylene-terephthalate (PET) bottles or polyester (PES) granulate) are transformed into fibers, which are manufactured into a fabric by adding the lining, membrane, and polyurethane glue. Adding the auxiliary products, the fabric is assembled into a ready-to-wear jacket (i.e., the garment). During the use phase, the retailer washes it in an industrial plant as a service. In the entire lifetime of the jacket (four years), it is washed three times. After the use phase, the zipper is dismantled for reuse. The remaining fabric is shredded and the PES is regranulated by a polymer melting process to be available for the next product loop. The material losses occurring in every manufacturing process (displayed by the process efficiencies given in percentage) are replaced by virgin PES, indicated by the orange box. includes five loops (i.e., one blue and four orange ones), the third scenario ten (i.e., one blue and nine orange ones). As previously described, this wear2 wearTM jacket system is compared to a (fictive) linear jacket that has the same components and is produced with the same technologies and process efficiencies. Hence, this linear product system is very similar to the one of the wear2 wearTM jacket (shown in Figure 2). There are only three main differences between the two.