2.1.3. Assumptions

The following points explain the reason for excluding some processes of the system:


#### 2.1.4. Description of the Scenarios under Study

Separate collection of the organic fraction has been implemented in the northern European countries for several years, and it is now relatively well established there. However, it is not ye<sup>t</sup> widespread in Spain or others countries of the southern Europe, although there is some experience at local or regional level. Therefore, the collection of the organic fraction currently coexists with the

collection of the bulky fraction. In this sense, this work assesses four scenarios (see Figure 4), which are based on the two waste collection systems described above and the waste fraction managed. Scenarios 1a and 2a represent the collection of the bulky fraction by means of the door-to-door and pneumatic waste collection systems, respectively, while in scenarios 1b and 2b the organic fraction is collected separately in the fifth container. In these scenarios, sensitivity analyses were carried out varying the effectiveness of the selective collection. Initially the study assumes that 100% of the organic fraction is disposed of in the fifth container. However, this ideal situation does not always occur. Therefore, in the sensitivity analysis this percentage was reduced, increasing the amount of biodegradable fraction in the bulky fraction. This bulky fraction is conducted to a sorting plant in order to recover the largest amount of organic matter. In this study, only 9.8% of the organic fraction was considered to be recovered from the bulky fraction, and the collection truck is considered to cover an average distance of 35 km to the sorting plant [46]. Finally, since the aim of the selective collection of the organic fraction is to convert it into high quality compost, the final destination of the organic fraction is a composting plant, which is located next to the sorting plant.

**Figure 4.** Diagram of selective waste collection scenarios under study.
