Page 309 - Materials Chemistry, Second Edition

4.6 Illustration of the Phase Impact Assessment by Practical Example 293

6. Weighting (Section 4.6.6):
Because weighting includes value choices, specifications for the basics of
weighting is indispensable for the credibility of an LCA.
7. Additional analysis of data quality:
Each step of the impact assessment should be accompanied by a critical
reflection of the quality of the data base. As described in Section 4.3.3.4,
the analysis of the data quality is explicitly required in the interpretation
(see Chapter 5).

4.6.1
Selection of Impact Categories – Indicators and Characterisation Factors

In the ‘definition of goal and scope’ of the illustrative study example the following
reasons are quoted for the selected impact categories:

The impact assessment in this study is based on the following impact
categories 369) :
A) Resource-related categories:
• Demand for fossil resources,
• Land use (forest).
B) Emission-related categories:
• Greenhouse effect,
• terrestrial eutrophication,
• acidification,
• summer smog
• aquatic eutrophication.

The separation of the impact category eutrophication into aquatic and
terrestrial eutrophication is in view of the different mechanisms of effect
within soil and water.
The mechanisms of effect for all categories considered (with the exception
of land use forest) are scientifically founded and they are usually convertible
from the inventory data. This is confirmed by their widespread use in national
and international LCAs. The general acceptance of these impact categories
can thus be presumed. 370) They can be considered as standard in the
common practice of LCA.

369) In the examined systems ozone destructive substances were not released in relevant quantities,
hence, for economic reasons this impact category was not considered.
370) In LCA practice it is hardly possible to make a complete estimate of all environmental issues.
In the present study by pre-selection of specific environmental issues a restriction is already
made. A desirable broad examination of as many environmental issues as possible is frequently
not done due to the different quality of the available inventory data and a differing scientific
acceptance of individual impact models.