3.3.1. Normalization Method Sensitivity Results

As described in Section 2.3.2, three different normalization methods were implemented for the values integrated into the weighted sum, which resulted in three different combinations: (a) min-max normalization, (b) z-score normalization and (c) proportionate normalization. For each of the above combinations, the sustainability index was calculated, and a ranking among the considered components was derived. In order to test the sensitivity of the final ranking to the applied normalization method, an equal weighting was considered. The rankings obtained from the three different combinations are listed in Table 6.


**Table 6.** Comparison of The Ranking Obtained from The Different Normalization Methods.

Based on the obtained rankings for the three different normalization methods, minmax normalization and z-score suggested the same ranking among the components. On the other hand, proportionate normalization led to a different ranking. Nevertheless, the first four places and the last one are identical to those obtained by the first two normalization methods. All normalization methods identified the virgin component, for which liquid hydrogen from a conventional source has been considered, as the most sustainable solution. On the other hand, the recycled component comprising randomly oriented fibers showed by far the lowest index, owing to its low quality; this highlights the need for upgrade technologies to improve quality and hence promote circularity and sustainability. Moreover, it is noteworthy that the recycled aligned component, for which liquid hydrogen from a conventional source has been accounted, ranks second; the latter applies to all three

normalization techniques. This can be attributed to its comparable to virgin quality, as well as to its environmental friendliness.
