**6. Lifecycle assesment methodology and selected environmental impact categories**

The life cycle assessment methodology takes into account all the impacts originated from the inputs and outputs of a system starting from the fiber cultivation/ production till the end of life of the jean, cradle to grave. An experimental study was conducted to represent the environmental impact of using recycled polymeric materials in a denim fabric in comparison to using virgin materials. In doing so, the methodology given in the authors' previous study was employed [88]. All of the calculations were performed from cradle to denim factory gate. Furthermore, the inventory was based on the 2020 denim production figures of a denim company in Turkey. As the assessment tool, SimaPro software, developed by the Pré Sustainability, was used. SimaPro is one of the leading Life cycle assessment (LCA) softwares that has been used for more than 25 years by the industry and academics in more than 80 countries. SimaPro uses two types of data: primary and secondary [91]. Primary data involves the basic specifications of a denim fabric, for example Article X, 150 cm in width and 14.89 oz./yd2 in weight.

This data is exclusive to the fabric production practices of the factory. Secondary data, however, comes from the database and it includes the impacts originated from producing that much raw material and all other inputs such as chemicals at

each stage. For the secondary data, Ecoinvent database that is embedded into the software and is the most common Life Cycle Inventory (LCI) database worldwide, was utilized [92]. To be able to perform life cycle assessment of a specific good or service, one needs to have inventory data for the complete supply chain. Due to the huge amount of data needed for this purpose, it is practically impossible to collect and organize the data of the complete background system. In that respect, the Ecoinvent database provides this very system fulfilling the data required for the assessment. The Ecoinvent v3 database contains Life Cycle Inventory (LCI) data taken from various sectors such as energy production, transport, building materials, production of chemicals, metal production and fruit and vegetables. The entire database consists of over 10,000 interlinked datasets, each of which describes a life cycle inventory on a process level [93]. SimaPro software provides six libraries that each contain all the processes that are found in the Ecoinvent database, but use different system models and contain either unit or system processes [94]. The three Ecoinvent system models are as follows: "allocations at point of substitution", "cut-off by classification" and "consequential". For life cycle assessment (LCA) of a product, the production of an item (e.g. denim fabric) is simulated, using both consumption/production (primary) data of a factory and the corresponding secondary data from the Ecoinvent database. The next step is to choose the environmental impacts to be calculated. The whole process is given in **Figure 6**.

**Figure 6.** *LCA calculation process.*

