Page 84 - Materials Chemistry, Second Edition

7 Goal Definition 69

results (Chap. 12). Often, several separate applications are intended in a study. For
example, the intended applications of the results of the illustrative case on window
frames in Chap. 39 were both to benchmark a new window design against three
windows already on the market and to identify hot spots in the life cycle of the
compared windows with the aim of guiding future impact reduction efforts.

7.3 Limitations Due to Methodological Choices

This aspect can be seen as a critical reflection of what the LCA results can and
cannot be used for. If a study only covers climate change (often referred to as a
“carbon footprint” study) it is, for example, important to stress that results cannot be
used to claim a general environmental superiority of a studied product or conclude
anything about its overall “environmental friendliness”. Also, if a comparative
study disregards one or more life cycle stages, it is important to stress how that
limits the interpretation of results. For example, a study comparing the production
of 1 tonne aluminum to the production of 1 tonne steel from mining to ingot cannot
be used to identify the environmentally soundest material for use in a car, because
the density difference of the two metals leads to differences in the amount of metal
used for the car body and differences in the car mileage (fuel consumption per
kilometre), causing different environmental impacts in the use stage and finally also
in the disposal stage. In the illustrative window frame case study (Chap. 39) a stated
limitation of the study was that a site-generic LCIA approach was taken in spite of
impacts being concentrated around Scandinavia, where the natural environments,
for some impact categories, do not correspond to the global average (e.g.
Scandinavian soils show a higher sensitivity to depositions of acidifying com-
pounds). Note that the limitations stated here should only relate to the choices made
in the goal and scope phases of an LCA (this chapter and Chap. 8). These choices
all relate to the planning and use of an LCA. On the contrary, choices made during
the inventory and impact assessment phases of an LCA (Chaps. 9 and 10) relate to
unforeseen constraints and assumptions (for example with respect to data avail-
ability) and must be documented at a later point in an LCA report, for example, in
the inventory analysis part (Chap. 9) or in the interpretation part of a report (see
Chap. 12).

7.4 Decision Context and Reasons for Carrying Out
the Study

This is an important aspect of the goal definition because it strongly influences the
appropriate elaboration of a life cycle inventory (Chap. 9). First, the reasons for
carrying out a study must be understood. The reasons should be clearly connected