Page 203 - Materials Chemistry, Second Edition

10 Life Cycle Impact Assessment 189

An absolute interpretation of LCA results (e.g. option A is sustainable, option B
is not) is not advisable as it requires a lot of additional assumptions.
• Best estimates: A fundamental value choice in LCA is not to be conservative,
precautionary or protective, but to focus on avoiding any bias between com-
pared scenarios by assuming average conditions, also referred to as best esti-
mates. Products or services assessed in LCA are typically not representing one
specific example (e.g. with a serial number or from a specific date), but an
average, often disregarding whether a specific life cycle process took place in
summer or winter, during the day or night, etc. As discussed by Pennington
et al. (2004), LCA is a comparative assessment methodology. Direct adoption of
conservative regulatory methodology and data is often not appropriate, and
should be avoided in LCIA in order not to bias comparison between impact
categories where different levels of precaution may be applied.

10.3 Optional Steps According to ISO 14040/14044
10.3.1 Normalisation

The indicator scores for the different midpoint indicators are expressed in units that
vary between impact categories and this makes it unfeasible to relate them to each
other and to decide which of them are large and which small. To support such
comparisons, it is necessary to put them into perspective, and this is the purpose of
the normalisation step, where the product system’s potential impacts are compared
to those of a reference system like a country, the world or an industrial sector. By
relating the different impact potentials to a common scale they can be expressed in
common units, which provide an impression of which of the environmental impact
potentials are large and which are small, relative to the reference system.
Normalisation can be useful for:
• Providing an impression of the relative magnitudes of the environmental impact
potentials
• Presenting the results in a form suitable for a subsequent weighting
• Controlling consistency and reliability
• Communicating results
Typical references are total impacts per impact category per:
• Geographical zone which can be global, continental, national, regional or local
• Inhabitant of a geographical zone (e.g. expressing the “environmental space”
occupied per average person)
• Industrial sector of a geographical zone (e.g. expressing the “environmental
space” occupied by this product system relative to similar industrial activities)