# Evaluation of the Circularity of Recycled PLA Filaments for 3D Printers
## 2 Scope and Objectives  
This paper focuses on the product level. There are indicators to measure the circularity of departments, companies, or organizations but they are out of our scope. Indicators help companies to classify and compare their products inside this new circular framework. In addition, it also becomes a criterion in the design processes. New products should  
Figure 1: Cycles in Circular Economy. Source: Ellen MacArthur Foundation [4]. become more and more circular (Figure 2). Finally, indicators help to position a band or a company inside the circular economy. The MCI focusing on restoring the material of the flows at the product and company level is based on the following six principles:  
1. Biological materials should come from sustainable sources. 2. Use feedback from recycled or reused sources. 3. Keep the goods in use longer (reusing, redistributing, increasing durability). 4. Reuse recycled components or materials after use
5. Intensive use of the products (via service, sharing or performance models). 6. Biological materials should remain biologically accessible and uncontaminated. With this scope, improving the MCI of a product or company does not necessarily mean improving the circularity of the whole company or system. However, an extended use of this methodology could be part of such improvement. The highest value proceeds from reusing components that keep all the functions and performances and are more valuable than recycled materials. MCI includes a factor representing the efficiency of the recycling process, while reuse is assumed to be 100% efficient. The debate is whether products are more circular if used for longer periods of time, even if they end up in landfill after use. The circular economy encompasses initiatives that can create a significant impact on material use, and case studies have shown that an increase in shelf life or greater intensity of use leads to substantial material savings (such as in reusable bottles). Longer lifetimes also allow for repair, reuse and/or resale (such as refillable products and second-hand stores) and are therefore correlated with the idea of increased circularity (Figure 2). In the development of MCI, the proportion of the product that is restored through component reuse and recycling (principles 2 and 3) and comes from recyclable and reusable sources is described as the restorative part, while the linear part of the flow refers to the proportion coming from virgin raw materials and ending up in landfill (or energy recovery). Principles 4 and 5 are treated as improvements in utility, an additional component in the calculation of MCI that depends on the linear part of the flow. The addition of biological materials  
Figure 2: Transition towards Circularity. to this methodology has required the introduction of principles 1 and 6. The first principle aims to ensure that the extraction of renewable materials from biological sources does not exceed the replenishment capacity of those materials by those sources. It also attempts to go further and regenerate natural systems. The sixth principle seeks to ensure that at the end of the life of biological materials, the nutrients they contain are returned usefully to the natural environment in a way that does not compromise the future ability of that source to create new materials. The MCI indicates how much of the materials that make up a product are circular, but it does not consider what materials they are or provide information on other impacts. Therefore, this methodology recommends using the MCI together with a group of complementary indicators. These indicators have been developed at the product level. MCI has the following differences and similarities with Life Cycle Assessment (LCA) methodologies. MCI is related of the use of materials throughout use. MCI aims to reuse or recycle materials or components so that we can increase the durability and the intensity use of the product. In the side, LCA is focused on the environmental impacts throughout the product life cycle for different scenarios.