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and requirements are provided for
Part 3: Scientific background 54 May 2001
calculating indicator results. Characterisation yields the ‘environmental profile’, consisting of a series of
‘indicator results’.
Besides the mandatory elements there are three optional elements. The first of these, ‘Normalisation’,
covers calculation of the magnitude of category indicators relative to reference information. In the second
optional element, ‘Grouping of indicator results’, impact categories are grouped into one or more sets
involving a descriptive sorting or a prioritising ranking. The third optional element is ‘Weighting’, i.e.
multiplication of indicator results or normalised results by numerical factors, with the aim of converting
and possibly aggregating indicator results across impact categories into a single score or a small
number of such scores. As a final optional element, ‘Data quality analysis’ may be performed to
enhance understanding of the significance, uncertainty and sensitivity of the LCIA results.
The mandatory and optional steps described above imply that different trajectories can be adopted en
route to the final LCIA result. These are illustrated in Figure 1.4.3.2.
selection
classification
characterisation
normalisation
grouping weighting
data quality analyis
Figure 1.4.3.2: Options for combining mandatory and optional ISO LCIA steps.
Part 3: Scientific background 55 May 2001
Based on ISO 14042, in this new Guide we distinguish the following steps of the Impact assessment
phase:
- [Procedures];1
- Selection of impact categories;
- Selection of characterisation methods: category indicators, characterisation models and
factors;
- Classification;
- Characterisation;
- Normalisation;
- Grouping;
- Weighting.
This structure is broadly similar to ISO 14042 (2000E). The main difference is that ‘Limitations of LCIA’
and ‘Comparative assertions disclosed to the public’ are not discussed here as separate steps of the
LCIA phase. The limitations of LCIA are treated in the general introduction to this Guide, under Goal and
scope definition and Interpretation: in the former, because the general limitations of LCA (including those
of LCIA) should be duly appreciated before conducting the actual LCA study and in the latter because
they put the conclusions into due perspective. Comparative assertions are one possible application of
LCA; this is determined in the Goal and scope definition phase and will steer several choices during the
LCA study (including the choice of simplified versus detailed LCA, application of weighting methods,
reporting guidelines, etc.). Issues for Interpretation (covering the ISO topic ‘Data quality analysis’),
reporting (covering ISO’s ‘Reporting’) and procedures (covering ISO’s ‘Critical review’) are treated in the
same way as in Goal and scope definition (see Section 1.4).
The selection of impact categories, category indicators and characterisation models has been broken
down into two steps, moreover, because these are clearly sequential elements.
Finally, this Guide does not entirely retain ISO’s distinction between mandatory and optional steps. The
Dutch LCA community feels that normalisation and data quality assessment (issues for Interpretation)
constitute at least recommended, if not mandatory, steps and that these should be part of any LCA
study.
The relation between the steps distinguished in this guide and the steps of ISO 14042 (2000E) is shown
in Figure 1.4.3.3.
 
1 Parallel to the treatment of this subject in the Goal and scope phase, “Procedures” is a separate step in Part
2a - Guide - but not in Part 3 - Scientific background.
Part 3: Scientific background 56 May 2001
Impact assessmentImpact assessment
Selection of impact
categories, category
indicators and
characterisation
models
Selection of impact
categories
Selection of
characterisation
methods: category
indicators,
characterisation
models and factors
Classification Classification
Characterisation Characterisation
Normalisation Normalisation
Grouping
Weighting
Grouping
Weighting
Procedures
Data quality analysis
Limitations of LCIA
Reporting and critical
review
Comparative
assertions disclosed
to the public
This Guide ISO 14042
Figure 1.4.3.3: The relation between the Impact assessment steps distinguished in this Guide and in
ISO 14042.
Part 3: Scientific background 57 May 2001
1.4.4 Interpretation
In ISO 14043 (2000E) the Interpretation phase is broken down into three elements:
- Identification of significant issues, based on the results of the LCI and LCIA phases of LCA;
- Evaluation, comprising completeness, sensitivity and consistency checks;
- Conclusions, recommendations and reporting.
Other elements of analysis, including a critical review, are considered additionally in clause 9 of ISO
14043.
Based on ISO 14043, in this Guide we distinguish the following steps of the Interpretation phase:
- [Procedures (Chapter 9 of ISO 14043)]1;
- Evaluation of results:
 consistency check
 completeness check
- Analysis of results:
 contribution analysis
 perturbation analysis
 sensitivity and uncertainty analysis
- Conclusion and recommendations.
This structure is broadly similar to ISO 14043. The main difference is that ‘Evaluation’ has been split into
two parts, one of which is placed before ‘Identification of significant issues’. The reason for this change
is that if there are large inconsistencies or errors in the data or if the data is very incomplete, all further
Interpretation steps become futile. A minor difference is the use of the term analysis instead of check for
the sensitivity and uncertainty analysis2. ‘Identification of significant issues’ is here operationalised in
two different steps: the contribution analysis and the perturbation analysis. Reporting and procedures
are treated in the same way as for the Goal and scope definition (see Section 1.4). For obvious reasons,
and to prevent endless iteration, issues for Interpretation is no longer included as an item in the
Interpretation phase itself.
The relation between the steps distinguished in this guide and the steps of ISO 14043 (2000E) is shown
in Figure 1.4.4.1.
There is an close relationship between the steps of the Interpretation phase and the other phases of the
LCA. On the one hand, there is input from the other phases, because these identify relevant issues for
Interpretation. On the other hand, the iterative nature of the LCA process allows for, and sometimes even
demands, making changes in prior phases, as when errors are found or results prove to be ‘too’ sensitive
to particular, debatable data, model choices, etc. during Interpretation.
 
1 Parallel to the treatment of this subject in the Goal and scope phase, “Procedures” is a separate step in Part
2a - Guidelines - but not in Part 3 - Scientific background.
2 Here, the term check is used to emphasise the fact that data or model choices are being checked, while the
term analysis is used for more complex assessments requiring dedicated tools and so on.
Part 3: Scientific background 58 May 2001
InterpretationInterpretation
Evaluation by
-completeness check
-sensitivity check
-consistency check
-other checks
Consistency check
Completeness check
Contribution analysis
Identification of
significant issuesPerturbation analysis
Conclusions,
recommendations
and reporting
Sensitivity and
uncertainty analysis
Conclusions and
recommendations
This Guide ISO 14043
Procedures
Evaluation of results
Analysis of results
Conclusions and
recommendations
Figure 1.4.4.1: The relation between the Interpretation steps distinguished in this Guide and in ISO
14043.
1.5 Further reading guidance
In the following chapters the steps distinguished above are discussed for each phase of LCA, viz. Goal
and scope definition, Inventory analysis, Impact assessment and Interpretation. Each step is discussed
according to a fixed format: ‘Topic’, ‘Developments