**4. Building a life cycle assessment (LCA) model for denim fabric manufacturing**

The motivation or the reason for doing denim LCA helps practitioners to structure their LCA model. The main framework for LCA studies is ISO 14040/44 standards [8, 9]. In addition, the communication way or tool of LCA study is also a determinative indicator for the construction of LCA study for such as determining the functional unit and the scope and/or system boundary of the study. A denim fabric mill

can perform a cradle to gate LCA study including the production of raw materials, transport of all materials to a factory, production steps and packaging of the final fabric or a gate-to-gate study to cover only production stages of the fabric.

Following an Environmental Product Declaration (EPD) format is another way of constructing an LCA study and communicating its results. Defined by ISO 14025, an EPD document is an ISO type III Environmental Declaration that reports comparable and third-party verified data about products and services' environmental performances from a lifecycle perspective [41]. EPDs are registered in the framework of a program and the study behind of an EPD is constructed according to these programs' Product Category Rules (PCR) guidelines and rules. The International EPD® System is one of the framework programs used for EPD construction and registration [42].

In the following sections, constructing a LCA model for denim fabric will be explained via a case study based on the production practices of denim fabrics by a Turkish denim mill.

### **4.1 Defining a functional unit/declared unit**

One of the fundamental steps of product LCA's is to define functional unit of the study. The selling unit for denim fabric is meters or yards depending on the market geography. The weight of the denim fabric is, on the other hand, communicated in oz./yd2 or gr/m2 units. And the width of the fabric determines how garment manufacturers place their cutting patterns on fabric and minimize their cutting waste and use optimum amount of fabrics. Therefore, using a weight unit as a functional unit in a fabric LCA is not feasible.

The PCR for the fabrics states that a declared unit for fabrics should be used instead of a functional unit as the fabrics are intermediate products with many different potential uses and a functional unit cannot be defined from functional aspects of a fabric. Therefore, m2 is used as the declared unit in fabric LCAs [43].

#### **4.2 The scope and system boundary**

As stated in Section 2.1, the scope of LCA studies are divided into four sections: cradle-to-gate (upstream), gate-to-gate(core), gate-to-grave(downstream) or cradleto-grave which covers all of the steps in the lifecycle. Denim fabrics are intermediate products that can be used in many different garment styles with the application of different washes. And the use and the life span of the denim garment vary for individuals (consumers) depending on their lifestyle, culture, geography, etc. This makes the construction of the use phase life cycle stage of a denim fabric very complicated and scenario-based.

Therefore, a fabric mill can choose to practice a cradle-to-gate LCA for their products covering the upstream processes including the production of raw materials and packaging materials and core processes including all relevant transport down to factory gate, energy, and water consumption during manufacturing operations by the denim mill including spinning, warping, sizing, weaving, finishing, rolling, and packaging processes (cradle-to-gate).

A representation of the system boundary of a cradle-to-gate and cradle-to-grave denim fabric LCA and activities covered within is given in **Figure 2**.

If a mill chooses to proceed with an EPD, the PCR should be followed when defining the system boundary. The life cycle stages with the relative modules are given in

*Life-Cycle Assessment as a Next Level of Transparency in Denim Manufacturing DOI: http://dx.doi.org/10.5772/intechopen.110763*

**Figure 2.** *System boundary of the LCA study.*

**Table 1**. In line with the system boundary, for EPDs the calculation procedure should also be separated into three life cycle stages as upstream processes (cradle-to-gate), core processes (gate-to-gate), and downstream processes (gate-to-grave) and shall be reported as such [43].
