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An aggregated life cycle sustainability index 379

effect of the global diets. In summary, the composite sustainability index and
aggregated sustainability index are innovative approaches to aggregate mul-
tidimensional indexes into the one or some comparable indexes to evaluate
sustainability (Gan et al., 2017). Computing aggregate values is a common
method used for constructing indices. An index can be either simple or
weighted depending on its purpose (Singh et al., 2012). Composite index
needs to be designed within a coherent framework to ensure the specific
parameters involved in the assessment process can change over time based
on the interests of the particular stakeholders.
However, despite the plenty outcomes for the application of composite
and aggregated sustainability index methods, there are two key gaps for life
cycle aggregated sustainability method (Ren et al., 2015b): (1) how to
address the qualitative criteria that are difficult to quantify in the social aspect
and (2) how to use the multidimensional LCSA results for decision making.
Ren (2018) developed a powerful method which can quantify the life
cycle aggregated sustainability of industrial systems by aggregating the data
of each alternative with respect to the evaluation criteria and the weights of
the criteria into a single sustainable index, and this method was employed in
this chapter to determine the sustainability sequences of three pathways for
bioethanol production (wheat-, corn-, and cassava-based bioethanol pro-
duction pathways) by using the life cycle aggregated sustainability
index method.

2 Life cycle aggregated sustainability index of three
biofuel production pathways

The method developed by Ren (2018) was employed to study the life sus-
tainability performances of three pathways for bioethanol production
including wheat-, corn-, and cassava-based options in Chinese conditions
(Ren et al., 2015b). The framework of multicriteria decision making for life
cycle sustainability assessment is shown in Fig. 14.1. The function unit is 1
ton bioethanol. The life cycle boundary of bioethanol systems is shown in
Fig. 14.2. The distance from the field to the plant for bioethanol production
and that from the plant to the market are assumed to be 300 and 500km,
respectively. The life cycle sustainability performances of these three scenar-
ios for bioethanol production are presented in Table 14.1 based on the work
of Ren et al. (2015b). It is apparent that all the data in the life cycle sustain-
ability performance matrix are crisp numbers, and they can be written in the
format of interval numbers, as presented in Table 14.2.