Page 204 - Materials Chemistry, Second Edition

188 4 Life Cycle Impact Assessment

impact category: Class representing environmental issues of concern to which
life cycle inventory analysis results may be assigned.impact category indicator:
Quantifiable representation of an impact category.characterisation factor: Factor
derived from a characterization model which is applied to convert an assigned
inventory analysis result to the common unit of the category indicator.

This terminology in ISO 14040 and 14044 is somewhat bulky and can best be
illustrated by an example. This is done for the scientifically best substantiated
impact category ‘climate change’ 18) (see also Section 4.5.2.2):
1. Impact category: Climate change.
2. Inventory results: Amount of a GHG per fU.
3. Characterisation model: Baseline model of 100 a of the International Panel of
Climate Change. 19)
−2
4. Category indicator: Infrared radiative forcing (W m ).
5. Characterisation factor: global warming potential (GWP 100 ) for each GHG (kg
20)
CO -equivalents/kg gas).
2
6. Category indicator result (unit): Kilograms of CO -equivalents per fU.
2
7. Category endpoints: for example, Coral reefs, forests, crops harvests. (It should
be noted here, that many, probably most, endpoints are not yet known. They
concern other obvious geological formations (glacier, arctic ice). Here changes
or disappearances will be of major importance to the living world including
humans.)
8. Environmental relevance: Infrared radiative forcing is a proxy for potential effects
on the climate, depending on the integrated atmospheric heat absorption
caused by emissions, and the heat absorption over time.
As ISO 14044 does not provide a list of impact categories, does not even recommend
one, the selection of the categories depends on the authors of the LCA. Table 4.2
shows two sample lists for a selection of impact categories. On the right side of the
table impact categories that can be assigned to the results of inventories (Mid-point
Categories), which can be further bundled (Damage Categories) are defined.
As the selection of impact categories must correspond to the goal and scope of
the study, the selection of categories should be made in the first phase of the LCA.
This is particularly important because the data to be procured in the inventory must
comply with the demands of the impact assessment. On the other hand, an LCA is
basically an iterative process for good reasons. Therefore the following approach is
recommended:
• Selection of impact categories plus category indicators as well as assignable
inventory parameters as far as possible in the first phase of LCA (definition of
goal and scope).
• Data collection in view of selected impact categories in the phase LCI analysis.

18) ISO (2006b, Table 1).
19) Intergovernmental Panel on Climate Change (IPCC).
20) GWP is not an impact category but a category indicator result.