Normalization is made in LCIA to indicate the relative significance
of the various environmental impacts of the LCA system, taking
into account the geographical area where the activities in the
LCA occur. In this final LCIA step, the previous characterized results
are divided by their respective normalized values and multiplied
by assigned ‘weights’ that give the relative importance of the particular
impact category. As illustrated in Fig. 6, this step allows the
individual impacts to be combined into a (dimensionless) final
score, or total impacts.
Weighting allows us to see the environmental trade-offs when
comparing different activities within the same life cycle study,
especially in the setting of priorities for pollution mitigation (Bengtsson
and Steen, 2000). There are several methods to assign
weighting values. SETAC workgroup on LCIA distinguished types
of weighting as:
monetary methods, such as society’s willingness to pay (for
environmental damage, illness, ecosystem disruptions);
sustainability and target methods, such as in the distance-totarget
procedure;
social and expert methods and/or panel approach.