172 Introduction to Renewable Biomaterials
Table 5.6Ecoindicator weighting values and survey responses (Goedkoop and
Spriensma, 2001).
Impact category Mean (%) Rounded (%) St. deviation (%) Median (%)
Human health 36 40 19 33
Ecosystem quality 43 40 20 33
Resources 21 20 14 23
100% 0%
10%
90%
Human health
Resources
Ecosystem health
20%
30%
40%
50%
60%
70%
80%
90%
0% 100%
100%90%80%70%60%50%40%30%20%10%0%
80%
70%
60%
50%
40%
30%
20%
10%
Figure 5.10LCA interest group response to weighting survey used for Eco-indicator 99 weighting
method (Goedkoop and Spriensma, 2001).
quality were twice as important as recourse use (Table 5.6). Figure 5.10 shows the
wide range of responses of this panel, which further illustrates the subjective nature of
weighting. United States-based weighting factors were also determined through survey
panel by Gloriaet al.(2007).
Since the act of weighting is subjective, various scientists have sought to create
methods that reduce the subject nature of a single score. One method employed
by Daystaret al.(2016)) tested the scenario outcomes using 16 different weighting
methods established by LCA experts, product producers, and product users. In some
results, the weighting factor can play a major role in influencing the results; however,
in Daystaret al.(2016), the results were generally the same when different weighting
methods were applied. A more robust approach to weighting and single score is the
stochastic multiattribute analysis (SMAA) (Prado-Lopezet al., 2014) where all possible
weighting factors are used in combination with internal normalization and uncertainty
data. This helps provide insight into whether the differences are significant between
options as well as the probability of one option resulting in a more favorable outcome
than another based on the range of weighting factors tested.
