## 2 Materials and Methods
### Eco + LCA Methodology  
In order to facilitate the incorporation of an LCA into the product design phase, a simple methodology (ECO + LCA) is proposed, which allows the designer to quickly analyse the multiple variables with environmental, economic, and social impact in the decisions made. This is the main contribution of designing a product with eco-design criteria (ISO 14006). The basis of this methodology is the compilation of an inventory that includes the different impacts derived from the different phases of the entire existence of a product, that is, the extraction of raw materials, transport, manufacture, use, product end of life, recovery, transport to landfill, and new raw materials. For this purpose, firstly, a block diagram with all the processes is generated, which indicates all the inputs, known as a product life cycle inventory. In the next step, the environmental impact of the different materials and processes that may be used in the manufacture of the product, inputs (resources), and outputs (emissions, products, by-products, and waste), are quantified in a table (see Table 1). There are different methods, some general and others sector-based, that classify impacts by a variable number of categories. For the purposes of this article, ReCiPe endpoint (hierarchist perspective) [48] has been used. The hierarchist perspective is the one with more scientific consensus in relation to the timeframe used to define the characterisation factors of the different impact categories analysed [48]. ReCiPe endpoint allows obtaining endpoint-oriented environmental impact categories that are easier to understand and interpret. Thus, a single environmental impact can be obtained with a quantitative assessment of environmental impact points. This avoids the need to work with different impact categories with results that are not comparable with each other, or to simply keep only one impact category, such as climate change, and disregard the rest. The software Simapro v9.2 [49] and the database Ecoinvent 3.7.1 [50] were used to obtain the environmental impact results. The software Simapro is a widely used, solid, and reliable tool that is commonly applied in life cycle analyses. Furthermore, it has the advantage of incorporating different globally accepted databases (e.g., Ecoinvent), which can be used as data sources to study the environmental impact of different materials and processes. The database Ecoinvent is one of the most used in the LCA field, as it incorporates a wide range of datasets, thus covering the basic aspects of any LCA. In addition, these datasets are localized in a way that a distinction can be made between geographical locations. For instance, different datasets can be selected to calculate the generated impact of generating 1 kWh of energy in Spain or in China. The environmental impact values in Tables 1-3 were obtained by using Simapro and selecting the corresponding dataset within the Ecoinvent database, that is, based on the material, process, transport, or waste treatment used in the specific product design. In addition to the environmental impact table for materials and processes, environmental impact tables for possible means of transport (see Table 2) and end-of-life (see Table 3) must also be made. From these tables, the designer will only have to fill in the data corresponding to each design to be analysed to automatically obtain the estimation of the environmental impact of the design. This allows the designer to perform as many iterations as necessary until a green design [51; 52; 53] product is obtained (see Table 4). In addition, for each alternative \begin{table}
\begin{tabular}{c c} \hline \hline
**Material/Process** & **Impact per Kg** \\ \hline Material 1 & XX \\ Material 2 & XX \\ Process 1 & XX \\ Process 2 & XX \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Environmental impact of materials and processes.