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in the last decade’, ‘Prospects’, ‘Conclusions’ and
‘Research recommendations’. However, as ‘Procedures’ is a fairly new topic in LCA with few
Part 3: Scientific background 59 May 2001
developments in the last decade to discuss, in this case this format is not particularly useful. The
Procedures step is therefore not discussed in each phase individually, but as an integrated whole in
Section 1.3. Another important issue to bear in mind while reading and using this Guide - and to stress
once more at this point - is that it has become clear in the preceding introduction that there is no such
thing as ‘a correct LCA’. The sophistication of an LCA and the way in which it is elaborated depend on
the specific situation in which LCA is being used as a decision support tool. In theory this might imply a
practitioner having to develop custom-tailored methods for each LCA study anew. From a practical angle,
however, this is obviously out of the question. Most choices vis-à-vis methods have broad ramifications,
restricting the choices available in other respects. One cannot first opt for a steady-state model and
subsequently opt for a change in capacity utilisation to supply the required inputs, as short-term and
long-term perspectives would then be mixed. Even if one agrees on the main purpose of the LCA study,
assuming that structural questions are to be answered there are still hundreds of choices to be made
before a well-founded LCA model has been constructed. This is clearly beyond the capabilities of most
practitioners and beyond the budget of most commissioners. To permit broad application of LCA some
degree of standardisation is therefore essential.
The standardisation developed in this Guide goes beyond the ISO standards, as the latter specify only
the general structure of LCA. True operationalisation involves so many choices that one can hardly
expect the world to agree on all of them and formulate them in an ISO standard. The basic question is
therefore: how to arrive at an operational LCA which at the same time providing the flexibility required for
widely differing applications. We have endeavoured to steer a ‘middle’ course, on the one hand excluding
certain applications and on the other specifying a number of standardised types of LCA and a framework
within which deviations from these can be accomplished in a transparent manner.
The first restriction has already been explained: the prime focus of this Guide is to support structural
decisions, using a long-term steady-state model for that purpose in the Inventory analysis phase and the
most apt (but more diverse) models in the Impact assessment phase. This does not mean that short-
term issues are deemed less important. It is merely our choice of focus, prompted by the aim of
supporting long-term sustainability developments.
Within these limitations, a wide variety of possible methods still remains available. We elaborate two
basic options in more or less systematic fashion.
- The first is a detailed LCA , which we believe to be representative for studies typically requiring
between 20 and 200 days of work. The detailed LCA is the baseline LCA elaborated in this Guide.
- The second is a simplified version of LCA, typically requiring between 1 and 20 days of work. In this
Guide we prescribe neither one option or the other, merely providing them as a ready reference
within the overall framework of issues and steps already specified. Appropriate sensitivity analyses
are also suggested. Practitioners wishing to deviate from the guidelines provided in this Guide for a
specific step are at liberty to do so, but should clearly justify their decision accordingly. One may,
for example, deviate from the economy-environment system boundary specified for detailed LCA, or
choose a different time horizon for leaching of landfill. Such options are not specifically supported in
this Guide, however, and their implementation is entirely the responsibility of the LCA practitioner. It
seems advisable, though, to introduce such deviations in the form of a sensitivity analysis of detailed
LCA, in order to retain reference to a more or less standardised type of LCA. Note that in a detailed
LCA certain steps may be performed at the simplified level, and within a single step, one may
indeed even opt to apply detailed guidelines for some unit processes or impact categories and
simplified guidelines for others. Finally, note that a simplified LCA is not simple in the sense of being
- Finally, on some topics an indication is provided of possible extensions for improving the quality of
detailed LCA in those respects where shortcomings are most obvious. A key example is the
absence of economic mechanisms in the LCA model, an unfortunate feature in cases where there
are extreme inelasticities of supply or demand. In the case of rechargeable batteries, for example, a
shift to non-cadmium types of battery will not result in a smaller influx of cadmium to the economy
and hence will not lead in the long run to reduced cadmium emissions. This is because the supply
of primary cadmium is extremely inelastic. In such a situation, LCA may yield a misleading
outcome. For a number of situations possible extensions are therefore specified, both within an
adapted LCA framework and as an addition to detailed LCA in Figure 1.5.1.
Part 3: Scientific background 60 May 2001
Simplified LCA
Detailed LCA
Figure 1.5.1: The relation between simplified LCA, detailed LCA and extensions.
In summary, simplified LCA and extensions build on detailed LCA, which is the baseline elaborated in
this Guide.
The guidelines for the various steps of LCA - the scientific background to which is provided in the present
Part - have not all been elaborated at the same operational level. The guidelines for one step may imply
that in each and every LCA study a number of actions should be actively performed, while those for
another step may imply that one need generally only follow the baseline proposals given in this Guide. In
the ‘Flow diagram‘ step, for example, a representative diagram of processes pertinent to the given LCA
study will have to be drawn up in each and every study, while in the ‘Selection of impact categories‘ step
the baseline proposal (see Section 4.2) can generally be followed time and time again. In the latter case,
one will of course have to evaluate whether the baseline proposal is sufficient, or whether other
categories beyond the baseline proposal should be added for the specific LCA study in question.
Below we present a ready-reference overview of the methodological steps distinguished in this Guide for
each phase of an LCA, with a reference to the section of the present Part dealing with each specific step
(Table 1.5.1).
Part 3: Scientific background 61 May 2001
Table 1.5.1: Overview of methodological steps distinguished in this Guide, with reference to the section of this part dealing with that specific step.
Phase Step Section in Part 3 Main result
Procedures 1.3
Goal definition 2.2
Scope definition 2.3
Goal and scope definiton
Function, functional unit, alternatives and reference flows 2.4
Functional unit;
alternatives compared
Procedures 1.3
Economy - environment system boundary 3.2
Flow diagram 3.3
Format and data categories 3.4
Data quality 3.5
Data collection and relating data to unit processes 3.6
Data validation 3.7
Cut-off and data estimation 3.8
Multifunctionality and allocation 3.9
Inventory analysis
Calculation method 3.10
Inventory table;
other indications (e.g. missing flows)
Procedures 1.3
Selection of impact categories 4.2
Selection of characterisation methods: category indicators,
characterisation models
Classification 4.4
Characterisation 4.5
Normalisation 4.6
Grouping 4.7
Impact assessment
Weighting 4.8
environmental profile;
Normalised environmental profile;
Weighting profile
Procedures 1.3
Consistency check 5.2
Completeness check 5.3
Contribution analysis 5.4
Perturbation analysis 5.5