## 2 Materials and Methods  
LCA is a well-established and situated methodology to assess the environmental performance of circular product systems. Thus, LCA is the method of choice in this study following the guidelines of the International Standards Organization [25]. The objective of the study is a comparison of the environmental performance of a circular jacket based on CE principles in comparison to a similar, but linear jacket. The jacket is in both cases water repelling and permeable to heat and moisture. The circular jacket is manufactured by the wear2 wearTM consortium ([[https://www.wear2](https://www.wear2) wear.org/]([https://www.wear2](https://www.wear2) wear.org/)) (accessed on 15 January 2021) (for more details, see Section 2.1). There are three main differences between the circular and linear jacket. The circular version has (1) a fabric that is partly made from polyethylene-terephthalate (PET) bottles while the linear jacket's fabric is made from virgin PES only, (2) a reusable zipper that is removed at the EoL, and (3) a recycling process that regranulates the entire fabric in order to be used for another jacket (so called closed loop recycling), instead of being incinerated. Note that the production of PET bottles for the circular jacket have caused environmental impacts themselves when produced. As PET bottles cannot be considered a waste stream in general--they are well recycled in many countries--an allocation approach must be chosen [26]. The 50/50 allocation rule for open-loop recycling from the Product Environmental Footprint (PEF) guide [27] is utilized for this study, meaning that 50%of the environmental impacts from the production of PET bottles are allocated to the wear2 wearTM jacket (for more information, please see the Supplementary Materials (SM)). The functional unit of this LCA is defined as \"use of a three-layer-laminate jacket, repellent to water and permeable to heat and moisture, for a period of four years\". Four years is the typical lifetime of a workwear jacket. The investigated jacket has the size large (L). The scope of the study includes all life cycle stages of the jackets. Figure 1 illustrates the system boundaries of the analysis. The necessary in- and output data of the defined system are collected from two general data sources. Mostly, case-specific unit process data collected from the partner companies are used in the life cycle inventory (LCI). Where no data were available (e.g., electricity mix used from the subsupplier of the zipper), generic data from a background database were used. For the modelling of the two systems, the LCA software tool SimaPro (version 9.1.1.1) together with version 3.6 (recycled-content system model) of the database ecoinvent ([[https://www.ecoinvent.org/](https://www.ecoinvent.org/)]([https://www.ecoinvent.org/](https://www.ecoinvent.org/))) (accessed on 15 January 2021) was used in this study. The Environmental Footprint (EF) version 3.0 is used as the life cycle impact assessment (LCIA) method. With the EF method, the product systems are evaluated in several midpoint impact categories in order to identify if burden-shifting of the environmental impact is taking place [28]. The following eleven impact categories are included: (1) global warming potential (GWP) in kg CO2-equivalent; (2) ozone depletion in kg CFC-11-eq. ; (3) ionizing radiation in kBq235U-eq. ; (4) photochemical ozone formation in kg Non-Methane Volatile Organic Compounds-eq. (NMVOC eq. ); (5) respiratory inorganics in kg PM2,5; (6) human toxicity (cancer) in Comparative Toxic Unit for humans (CTUh); (7) acidification of soil  
Figure 1: The system boundaries as set for this study. All the life cycle stages are included for the production of a three-layer laminate jacket. For the black boxes, primary data is collected directly from the partner companies.