Page 46 - Materials Chemistry, Second Edition

30 2 Goal and Scope Definition

To the first point, great progress has already been made by the International
Standardisation (see Section 1.4). To the second, a uniform data format for data
7)
bases and data communication has been initiated. To the third criterion, no
general presetting can be provided because system boundaries depend on the
specific problem in question. If, for example, a product is manufactured only
in Italy using native raw materials and pre-products and distributed solely in
Italy, the European Union as geographical system boundary makes little sense.
Nevertheless, in the component LCIA, transnational emissions and their respective
potential impacts have to be considered (see Chapter 4). In this context, as in LCA
everywhere, transparency is very important (see Section 5.4).
The necessity for cut-off criteria, regulating the exclusion of insignificant inputs
into the product system, results from the following consideration:
Product systems are embedded into the large systems ‘technosphere’ and
8)
‘environment’. It is a fundamental realisation of system analysis that all
subsystems are linked, even though more or less intensely. To be able to
study a subsystem for itself, numerous less important links must be broken.
For this, rules are necessary. An important rule states that, for example, the
infrastructure (roads, rails, etc.) is usually neglected (there are important
9)
exceptions, however). Something similar is true for capital goods (e.g. the
production of machines to manufacture the products), provided these are
not the ones to be compared in a study.
ISO 14044 10) states three cut-off criteria applied for the entire product system as
well as for individual unit processes:
1. mass
2. energy
3. environmental relevance.
Often, a proportion of 1% (mass, energy, etc.) of the overall system is chosen
as the cut-off criterion. If a first analysis has, for example, shown that for the
manufacture of a product 12 different materials are needed, their percentage ratio
is determined in a first step. In the fictitious example of Figure 2.2, component
ratios of 5, 6, 9 and 12 are below 1%. The cut-off criterion ‘mass < 1%’ alone entails
that these components are not balanced over their entire life cycle. However, a
first estimation of the energy consumption shows that component 9 has a mass
ratio of only 0.2%, although for its production, 2.7% of the total energy is needed.
Therefore, component 9 would be examined through its entire life cycle.
In addition, the rule is often applied that the portion to be cut off shall not exceed
5% per unit process (one box in the product tree). In Figure 2.3, a unit process with

7) ISO (2002) and EC (2010).
8) Both together result in the world in which we live; the technosphere, according to this
functional definition, is ‘everything under human control’, and the environment is ‘all that is
not technosphere’. Frische et al. (1982) and Kl¨ opffer (1989, 2001).
9) Frischknecht et al. (2004, 2005).
10) ISO (2006b, Section 4.2.3.3.3).