**1. Introduction**

As UN Secretary-General António Guterres said at Conference of the Parties (COP) on November 20th, 2022, the world should take more action to drastically reduce emissions immediately [1]. Unfortunately, action to transform the business practices continues to stay incremental, including the ones in the fashion industry. According to the Business of Fashion Sustainability Index 2022, the biggest players in the industry are still moving too slowly to achieve the set targets by 2030 [2]. Fashion brands need to measure their social and environmental impact continuously and act vigorously to decrease them. Consumer communication remains vital in this process

with a certain level of transparency to lead to the desired change. However, "Green Washing" appears as a threat to real action as marketing activities without any solid and provable data become common practices for many brands in the fashion industry.

Life cycle assessment (LCA) methodology serves as a solution to "Green Washing" and represents the next level of transparency since LCA can help brands collect, analyze and monitor their sustainability performance with science-based results. Sustainable fibers and certified materials occur to be the most important choice for brands who would like to have green claims [3]. Although materials represent a significant role in the calculation of overall environmental impact of the products, other input and process parameters also are important in the overall calculation.

This chapter addresses the impact of the textile industry and processes, and the denim-related LCA studies first. It, then, offers a framework on how to build an LCA model in denim fabric manufacturing and use data to compare different products and production practices in this very industry.
