Page 47 - Materials Chemistry, Second Edition

28 LIFE CYCLE ASSESSMENT HANDBOOK

• Conclusions, limitations, and recommendations.
• Appropriateness of the definitions of the system functions, the
functional unit and system boundary;
• Limitations identified by the data quality assessment and the
sensitivity analysis.

The text of ISO on interpretation is very concise, and no details are given on
procedures and techniques to be employed. The same applies to most guide-
books on LCA. They mention carrying out an uncertainty analysis, but give no
clear guidance on how this should be done.
In another context, we have introduced the distinction between procedural
and numerical approaches [3]:

• Procedural approaches include all types of analyses that deal with
the data and results in relation to other sources of information,
like expert judgement, reports on similar products, intuition,
reputation of data suppliers, and so on.
• Numerical approaches include those approaches that somehow
deal with the data that is used during the calculations, without
reference to those other sources of information, but as algorithms
that use and process the data in different ways, so as to produce
different types of "smart" data reduction that provide an indication
of reliability, key issues, discernibility, robustness, and so on.

This distinction helps us understand some important roles of interpretation.
On the one hand, it is about comparing the data and results with previous
findings, and putting the results in the context of decision-making and limita-
tions. On the other hand, it is devoted to a systematic analysis with the help
of statistical and other decision-analytic techniques. The latter type may be
incorporated in software, and indeed, an increasing number of software pack-
ages contain options for running Monte Carlo analysis, doing sensitivity anal-
ysis, carrying out statistical significance tests, etc. For instance, in the CMLCA
software, we have implemented, among others:

• Contribution analysis;
• Comparative analysis;
• Uncertainty analysis;
• Perturbation analysis;
• Key issue analysis;
• Discernibility analysis.

The iterative nature of the ISO framework (Figure 2.1) shows up in this con-
text. Whenever the uncertainties are too high, we may go back to collect better
data. Whenever sensitivity analysis shows that some decisions are crucial, we
may go back and do a more refined analysis. In this way, the interpretation
helps to prepare for a balanced decision, while helping improve the LCA.