Page 96 - Materials Chemistry, Second Edition

8 Scope Definition 81

The background system, in contrast, is commonly defined as those processes of a
system that are not specific to it. Such processes take part in numerous product
systems besides the one studied. Examples are society’s electricity supply, the
production of metallic copper, or the waste management systems. Neither of these
is specific to the product under study, but typically purchased in a market without
possibility to choose between specified individual suppliers. The background sys-
tem is typically modelled using LCI databases, which contain average industry data
representing the process in specific nations or regions. From a management per-
spective, processes in the background system can typically not be structurally
changed by the decision-maker commissioning a study (e.g. a company), because
the decision-maker is only a minor customer and therefore can only exert limited
power or because the suppliers are anonymous to the customer like the case of
copper which is bought on the global metal market (an exception is Situation B
studies where the decision-maker has influencing power on the background system,
see Chap. 7). The distinction between foreground and background system is
especially useful for planning data collection for the inventory analysis (see Chap. 9)
and for making recommendations as part of the interpretation of LCA results
(see Chap. 12).

8.2.4 Life Cycle Inventory Model and Results

A life cycle inventory (LCI) model aims to link all unit processes that are required
to deliver the product(s) studied in an LCA (glueing together the product system).
Figure 8.3 shows an example of an LCI model for a generic product.
An LCI result is an inventory of the aggregated quantities of elementary flows,
separated into resources and emissions, from all the unit processes within the
system boundary. These elementary flow quantities must be correctly scaled to the
assessed product by considering the extent to which the function of each unit
process is required to deliver the studied product (see Chap. 9).

8.2.5 Life Cycle Impact Assessment

LCIA is composed of selection of impact categories, classification and characteri-
sation, normalisation and weighting (the latter two are optional steps according to
ISO). Chapter 10 details these steps and only their main characteristics and pur-
poses are presented here.
Selection of Impact Categories, Classification and Characterisation
The first step of LCIA involves selecting the impact categories that are relevant to
consider in the LCA (considering the goal and scope of the study) and classifying
the elementary flows of the LCI results into these impact categories.