Page 63 - Materials Chemistry, Second Edition

LIFE CYCLE INVENTORY MODELING IN PRACTICE 45

• Comparative Analysis - External Use of Results
• Provide science-based defense to public concerns or criticisms
of a product's environmental performance compared to alter-
natives, including proposed legislation or bans
• Use LCA results as the basis for marketing statements compar-
ing a company's product with competing products

It is recommended, and in some cases required, that studies intended for
external use undergo a critical review. For environmental product declara-
tions prepared under product category rules, the program operator generally
defines the peer review process. Critical review by a panel of interested parties
is required for LCAs intended to be used as the basis for public comparative
claims about the environmental superiority of one system over another [2].

3.3 Scope

Once the study goal has been defined, scoping decisions can be made. The
breadth and level of detail of the study must be sufficient to ensure that the
stated goals have been addressed. Key aspects of the scoping phase include
defining the product system(s) to be studied, the functional unit, the system
boundaries (in terms of life cycle stages as well as time and geographic bound-
aries), methodological issues such as allocation procedures, impact categories
to be included, impact assessment method, and need for critical review. As the
project proceeds, some of the initial goals (such as goals for age of data used,
industry coverage, etc.) may not be met, as they may be subject to data avail-
ability and practical constraints on project budget and timing. It is important
to document not only the intended goals but also the limitations that were
encountered in conducting the analysis and assumptions or estimates that
were made.

3.3.1 Functional Unit
As defined in ISO 14040, "The functional unit defines the quantification of the
identified functions (performance characteristics) of the product. The primary
purpose of a functional unit is to provide a reference to which the inputs and
outputs are related. This reference is necessary to ensure comparability of LCA
results" [1].
If the goal of the project is to develop an environmental profile for an indi-
vidual material, then the functional unit can be very simple, e.g., output of
a kilogram (kg) of material or a megajoule (MJ) of a fuel. However, defining
the functional unit for comparative analyses of products can become quite
complicated.
In a comparative analysis, the functional unit must take into account
differences in the properties of the product, such as strength or durability,