Page 128 - Materials Chemistry, Second Edition

8 Scope Definition 113

categories in LCA software essentially takes the same time as calculating results for
a single impact category.
For some LCA studies, no LCIA method may cover an environmental impact
that is considered relevant. In such cases, the LCA practitioner can choose to
develop an LCIA method on their own and this development should be guided by
the six criteria above. Often, however, the development of a new impact category is
not feasible for an LCA practitioner, due to budget constraints and limited
knowledge of the impact pathway. The potentially relevant environmental impacts
that are not covered by the impact assessment should be highlighted in the scope
definition and considered qualitatively in the interpretation of results (Chap. 12).
An important aspect related to compatibility between the collected elementary
flow of the life cycle inventory analysis and the ensuing LCIA is the degree of
spatial differentiation of the LCA study. Spatial differentiation essentially means
taking into account where an elementary flow occurs. This information is relevant
for many impact categories, because the sensitivity of the environment towards 1
unit of elementary flow differs from place to place (see more details in Chap. 10).
Many popular LCIA methods are (still) spatially generic. Yet, spatially differenti-
ated methods have over the years increased in numbers and quality and their use
may therefore increase in the future. If it is chosen to use spatially differentiated
methods it is important to collect spatial information for the elementary flows in the
life cycle inventory analysis (e.g. name of nation, watershed ID or grid cell defined
by GIS coordinates) that is compatible with these methods.
Normalisation and weighting are optional LCIA steps under ISO 14044:2006,
and as part of the scope definition the LCA practitioner should decide whether
normalisation and weighting is needed. Are the steps relevant for the intended
application(s) and target audience of the LCA study (see Goal definition in Chap. 7)?
Normalisation is usually beneficial to aid the understanding of results if the target
audience are not experts, and weighting is required if an aggregation of impact
scores across the environmental impact categories is intended. On top of normali-
sation, an LCA practitioner may thus choose to include weighting, if the commis-
sioner of a study has specifically asked for single score results. The decision to
perform normalisation and weighting can also influence the choice of LCIA method
since not all methods support these steps. A detailed description of normalisation and
weighting is given in Chap. 10.

8.9 Special Requirements for System Comparisons

Many LCA studies compare systems, e.g. when two or more products fulfil the
same function as captured in the functional unit. The ISO 14044 standard poses a
number of special requirements for the scope definition of comparative studies to
ensure that the systems can actually be compared: “Systems shall be compared
using the same functional unit and equivalent methodological considerations, such
as performance, system boundary, data quality, allocation procedures, decision