**3. Materials and Methods**

#### *3.1. Object and Plan of Analysis*

The objects of the study were two 205/55/R16 tires designated for use in passenger cars. The first specimen was produced using a traditional manufacturing technology, the other was the modern eco-tire.

Until recently, the first three stages of the tire life cycle (design, manufacturing, and use) were of interest to people only in the economic dimension. The framework for the minimization of the environmental impact occurring in the life cycle of industrial products is rooted in the concept of Life Cycle Thinking (LCT). It is one of the concepts recommended by the European Commission that are instrumental in achieving sustainable development. Its purpose is to foster positive change in manufacturing by reducing the environmental impact of processes and manufactured products. Currently, the EU is promoting mechanisms aimed at stimulating the manufacturing of environmentally sound products with a view to improve the condition of the European natural environment and boost the attractiveness and position of EU in the world. Therefore, the notion of seeking methods to minimize the environmental impact of products and services throughout their entire life cycle is consistent with

the policies of the European Commission. The basic assumption is to implement intervention measures predominantly at the life cycle stages that exhibit the highest potential for reducing the negative impact on the environment [29–32]. Therefore, the focus of this work is on establishing which stages and factors of the car tire life cycle display the biggest potential for sustainability-driven improvement. From the design, to manufacture, utilization, and to post-consumer waste management, a product life is essentially a cycle, which is why the term "life cycle" is commonly applied to all products, including car tires. The concept of life cycle management (LCM) has an important practical dimension, but at the same time it is a way to introduce life cycle thinking into business practices. Its main goal is to manage the company's operations and its products in such a way as to ensure more and more sustainable production and consumption [33,34]. A growing concern for nature leads to the development and use of increasingly complex methods to reduce the burden on the environment, hence, the development of methodologies for the assessment of the environmental impact of processes, products, and industries. One of the methods in question, the Life Cycle Assessment (LCA), applies a holistic approach to the product, which includes its impact from the acquisition of raw materials, through production and use, to final post-consumer waste utilization. It covers the environmental impact of all life cycle stages and is in line with the principles of sustainable development [35–38].

The point of reference for the analysis carried out in the subsequent sections was provided by the regulations and recommendations set out in the ISO 14040 group of International Standards. All four LCA phases were completed: the goal and scope definition, inventory analysis, impact assessment, and interpretation (Figure 2) [31].

**Figure 2.** Four phases of the Life Cycle Assessment (LCA) study. Own work based on [31,39].

#### *3.2. Four Steps of the Analysis*

One of the possible applications of the LCA method is the assessment of production technology from the point of view of its impact on the natural environment. The aim of the analysis was to compare the environmental impacts associated with the life cycle of two different types of tires based on different manufacturing technologies. Therefore, the conducted analysis is classified as a type of comparative analysis. It has been used to determine whether there are differences in the magnitude of the environmental impact generated during the life cycles of selected car tires produced based on two different technologies. The change of the production technology of traditional tires to ecological tires has taken place in the last few years and is mainly related to the materials and materials used in their production. The key issues of the conducted analysis concern environmental effects [36,39]. The goal of the analysis was firstly to provide the description of the status quo of the industry (retrospective LCA), and secondly, to study the potential future consequences and determine recommendations for the development of more environmentally friendly solutions (prospective LCA). The procedure follows an LCA methodology whose purpose is to determine the extent of the negative environmental

impact of a given object's life cycle. To that end, all four LCA phases were conducted. In the LCA analysis, two terms are particularly important: function and functional unit. In many cases, it is not possible to simply compare product A and product B as they may have different performance characteristics. The system boundaries are not always easy to define and the assumptions made during the process maybe not consistent, resulting in challenges when comparing between different results. Moreover, in most of the published cases of study, the LCA of a process, product, or service is retrospective (measured/estimated data) rather than prospective (forecasted data). Therefore, it does not typically relate to broad steps such as design, development, research, and education that can tremendously change the life cycle or even improving it by considering the prevention or reduction of manufacturing [38,39]. In a general sense, the analysis serves to estimate the potential environmental burden associated with the way that a given product performs its specific function. If possible and justified, a time frame should also be included in the functional unit. The functional unit is the quantified performance of a product system that serves as the reference unit in the life cycle analysis. The reference flow is a measure of the outputs from processes in the product system required to perform the function expressed by the functional unit. If the LCA analysis covers the entire life cycle, it is recommended that the functional unit from the product use stage be considered, as it will most comprehensively express and capture the essence of the function [40].

Due to the fact that both the analyzed products in this study are passenger vehicle tires performing in the same area of applications, it was resolved that the function would refer to this aspect. It was defined as covering the distance of 50,000 kilometers over a period of 5 years in an average style of driving.

The key issue investigated in the course of this analysis was to highlight the differences in the environmental burden between the two products that result from changes in the manufacturing process and raw materials consumed by their production processes. The geographic and time frame of the data was the same and it was the technological scope that was different. Given that the company providing the data is in Europe and has a well-established position on the market, the considered geographic range is also Europe. The time frame encompassed the same range because both traditional and ecological car tires are currently in continuous production. From the spatial dimension perspective, no relevant impact is noted since both products are produced at the same tire manufacturing site, however, with the implementation of different production methods. This is the technology of manufacturing—traditional or ecological—that produces tires of specific and different parameters. Making certain exclusions in LCA analyses is almost always necessary. The cut-off criteria are either specified by value choices or may be dictated by independent factors, such as data gaps. In any case, several parameters are distinguished for specifying the cut-off rules, the most popular of which are exemptions based on the criterion of the mass percentage share in the total physical output and the percentage share in the total economic value of the output. The cut-off criteria enable selecting and specifying the key elements of the system and simplify both the model and the analysis. However, the exclusions should be clearly defined and described [41–43]. Storage, distribution, sales, and technical testing processes were outside of the scope of this study.
