Page 207 - Materials Chemistry, Second Edition

10 Life Cycle Impact Assessment 193

• Aggregating impact scores into several or one single indicator (note that
according to ISO 14040/14044 there is no scientific basis on which to reduce the
results of an LCA to a single result or score because of the underlying ethical
value-choices)
• Comparing across impact categories
• Communicating results applying an underlying prioritisation of ethical values
Note that in all of these cases weighting is applied, either implicitly or explicitly!
Even when applying no explicit weighting factors in the aggregation by simply
summing up impact scores, there is always an implicit equal weighting (all
weighting factors = 1) inherently applied when doing any of the above. According
to ISO 14044, weighting is not permitted in a comparative assertion disclosed to the
public and weighted results should always be reported together with the
non-weighted ones in order to maintain transparency. The weighting scheme used
in an LCA needs to be in accordance with the goal and scope definition. This
implies that the target group including their preferences and the decisions intended
to be supported by the study need to be considered, making shared values crucial
for the acceptance of the results of the LCA. This can pose important problems due
to the variety of possible values among stakeholders, including:
• Shareholders
• Customers
• Employees
• Retailers
• Authorities
• Neighbours
• Insurance companies
• NGOs (opinion leaders)
• …
It may not be possible to arrive at weighting factors that will reflect the values of
all stakeholders so focus will typically have to be on the most important stake-
holders, but is it possible to develop one set of weighting factors that they will all
agree on? If this is not the case, several sets of weighting factors may have to be
applied, representing the preferences of the most important stakeholder groups.
Sometimes the use of the different sets will lead to the same final recommendations
which may then satisfy all the main stakeholders. When this is not the case, a
further prioritisation of the stakeholders is needed, or the analysed product system
(s) must be altered in a way that allows an unambiguous recommendation across the
applied weighting sets.
The weighting of midpoint indicators should not be purely value-based. More, to
some extent, science-based criteria for importance of environmental impacts may be:

• Probability of the modelled consequences, how certain are we on the modelled
cause–effect relations?
• What is the resilience of the affected systems?