Page 98 - Materials Chemistry, Second Edition

8 Scope Definition 83

ensure reproducibility of the LCA study and potentially allow elements of the
underlying LCI model to be used as data sources for other LCA studies, if results
are publicly released. LCIA results must be documented by the numerical values of
the characterised results for each impact category covered. If normalisation and
weighting of characterised results is carried out (see Sect. 8.2.5) the results of these
steps must also be documented numerically.

8.4 Object of Assessment

8.4.1 Functions

All LCAs study one or more product systems composed of many unit processes that
are active throughout the life cycles of the product system(s). To study these
systems the functions they provide must be understood. Indeed, LCA is the envi-
ronmental assessment of needs fulfilment focusing on functions first and then on the
products needed to provide these functions. An LCA study should thus first define
the functions from the perspective of the user (later the perspective will change
when secondary functions are to be defined, see Sect. 8.5). For example, two
different energy technologies may be compared on the basis of the function they
provide of enabling the delivery of electricity to households (through a common
distribution system). Functions are especially important to understand when com-
paring two or more product systems because a comparison is only fair and
meaningful if the compared systems provide (roughly) the same function(s) to the
user. For example, a tablet and a newspaper both provide the function of a news
media, but because the tablet provides more functions (access to other websites,
word processing and other software) a direct comparison of environmental impacts
of a newspaper and a tablet would not be meaningful. An LCA must therefore
always be anchored in a precise, quantitative description of the function(s) provided
by the analysed product system. In the illustrative case on window frames in
Chap. 39, the windows are compared based on their function of allowing daylight
into a building.

8.4.2 Functional Unit

To support a fair and relevant quantitative comparison of alternative ways of
providing a function, knowledge of the functions provided by the alternative pro-
duct systems must be used to define a functional unit. A functional unit defines the
qualitative aspects and quantifies the quantitative aspects of the function, which
generally involves answering the questions “what?”, “how much?”, “for how
long/how many times?”, “where” and “how well?”. For example, a comparison of