Page 66 - Materials Chemistry, Second Edition

L1644_C02.fm Page 43 Tuesday, October 21, 2003 3:07 PM

1. Data collection, which includes the specification of all input and output
flows of the processes within the product system (product flows, i.e., flows
to other unit processes, and elementary flows from and to the environment)
2. Normalization to the functional unit, which means that all data collected
are quantitatively related to one quantitative output of the product system
under study; usually, 1 kg of material is chosen, but often other units such
as a car or 1 km of mobility are preferable
3. Allocation, which means the distribution of emissions and resource extrac-
tions within a given process throughout its different products, e.g., petro-
leum refining providing naphtha, gasolines, heavy oils, etc.
4. Data evaluation, which involves a quality assessment of the data (e.g., by
eventually performing a sensitivity analysis)

The result of the inventory analysis, consisting of the elementary flows related to
the functional unit, is often called the life-cycle inventory table.

2.2.3 IMPACT ASSESSMENT
The impact assessment phase aims at making the results from the inventory analysis
(IA) more understandable and more manageable in relation to human health, the
availability of resources, and the natural environment. To accomplish this, the inven-
tory table will be converted into a smaller number of indicators. The mandatory
steps to be taken in this regard are:

1. Select and define impact categories, which are classes of a selected number
of environmental impacts such as global warming, acidification, etc.
2. Classify by assigning the results from the IA to the relevant impact
categories.
3. Characterize by aggregating the inventory results in terms of adequate
factors (so-called characterization factors) of different types of substances
within the impact categories; therefore a common unit is defined for each
category. The results of the characterization step are known as the envi-
ronmental profile of the product system.

More details will be given in Chapter 3.

2.2.4 INTERPRETATION
The interpretation phase aims to evaluate the results from the inventory analysis or
impact assessment and compare them with the goal of the study defined in the first
phase. The following steps can be distinguished within this phase:

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