Page 137 - Biofuels for a More Sustainable Future

124 Biofuels for a More Sustainable Future

more detail, such as Azapagic (2011). However, in this chapter we will con-
sider to the phases “Goal and Scope Definition” and some elements of
“Impact Assessment” as they provide a useful basis for the initial stages of
a sustainability assessment and for the environmental indicators, respectively.
The Goal and Scope Definition phase of LCA has three major functions,
all of which are equally applicable to LCSA:
1. Define the purpose of the study
• While quite self-explanatory, it is nevertheless important to identify
exactly what the purpose of the assessment is for. Is it to compare one
product to a competitor? To benchmark the impacts of a new pro-
duction process? Or to identify improvement opportunities in exist-
ing products or processes? Each of these may lead to different
methodological choices. For instance, if comparison to other systems
is required, the practitioner should be careful to define those other
systems such that they provide a genuinely equivalent output. This
is closely related to the concept of “functional unit”, which is dis-
cussed as follows.
2. Define the system boundaries
• The system boundary describes the physical scope of the assessment,
that is, the parts of the life cycle which are or are not accounted for.
This can take several forms depending on what is most appropriate
for the system under assessment and the purpose of the study. The
most common system boundaries for LCA are “cradle-to-gate”
and “cradle-to-grave”, as depicted in Fig. 5.4.
It should be noted that other system boundaries are possible and may be rel-
evant depending on the system under study. For instance, processes seeking
to close the material circularity loop by encompassing recycling and rema-
nufacturing might take a “cradle-to-cradle” or “gate-to-gate” approach.
Whatever the system boundary chosen, it is critical that it is transparent
to readers in order to avoid misinterpretation.
3. Define the functional unit
• The functional unit defines the function of the system and enables
comparison of different systems on an equivalent basis. For instance,
the function of beverage packaging is to store a certain amount of
beverage, but this same function might be provided by 600g of glass
or 35g of PET. Consequently, an appropriate functional unit might
be “beverage packaging for 1L of water”, as opposed to “1 kg of bot-
tles”, in order to ensure that the comparator systems are functionally
equivalent.