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the process.
1.4 Stepwise structure for Environmental Life-Cycle Assessment
As already mentioned in Chapter 1, this Guide adheres rigidly to the four main phases of LCA specified
by ISO (see ). In this Guide we elaborate a logical, stepwise structure for each of these four phases,
based on general practical experience of the logical sequence of actions undertaken in the course of an
LCA study. In naming the steps we have taken the ISO phraseology1 as our point of departure wherever
possible. No iterations are specified in the Guide, for in principle the outcome of any step may lead to a
revision of previous steps. In practice, iteration between steps will be so frequent and manifest itself in
so many different ways that it would be impossible to elaborate them all in a guide. In this sense, the
described steps specify a logically ordered structure that allows for any degree of iteration desired.
Procedural aspects with broader ramifications are specified for each phase separately.
1 This does not imply that the authors consider ISO phraseology to be the most appropriate in all cases.
However, deviation from the ISO wording would probably not be helpful in achieving an understandable and
widely acceptable Guide.
1.4.1 Goal and scope definition
ISO 14041 (1998E) breaks down the Goal and scope definition phase of an LCA into the following steps
or elements (clause 5, p.4):
- Goal of the study;
- Scope of the study;
- Function, functional unit and reference flow;
- Initial system boundaries;
- Description of data categories;
- Criteria for initial inclusion of inputs and outputs;
- Data quality requirements;
- Critical review;
- Study report.
Part 3: Scientific background 47 May 2001
Based on a review of steps and items proposed for the Goal and scope definition phase by ISO 14040
(1997E) ISO 14041 (1998E), Heijungs et al. (1992), Lindfors et al. (1995a) and Wenzel et al. (1997), we
propose to distinguish the following steps for Goal and scope definition:
- [Procedures];1
- Goal definition;
- Scope definition;
- Function, functional unit, alternatives and reference flows.
Although the structure is broadly similar to ISO 14041 (1998E), there are several differences and
1. Procedures covers the ISO element ‘Critical review’, but is a more general term indicating the
possible usefulness of covering other procedural aspects like stakeholder participation in a particular
LCA study. In the present Guide guidelines on this topic are given for each individual LCA phase and
the Procedures step therefore also recurs in the Inventory analysis, Impact assessment and
Interpretation phases. However, in Part 3 - Scientific Background (this document) - Procedures are
not discussed for each step separately but in a single, comprehensive section of this chapter
(Section 1.3). This is because ‘Procedures’ is a relatively new topic and it is not yet particularly
useful to discuss developments since 1992 for each LCA phase individually. A separate background
study has been devoted to the topic (De Bruijn & Van Duin, 1998; Van Duin & De Bruijn, 1998).
2. To the ISO step ‘Function, functional unit and reference flow’ the choice of alternatives has been
added in order to emphasise that it is here that selection of (product) systems for comparison takes
place, if relevant in a given LCA study.
3. Initial system boundaries, description of data categories, criteria for inclusion of inputs and outputs
and data quality requirements now constitute elements of the Inventory analysis.
4. In each step distinct guidelines are given for reporting and for issues for Interpretation. Rather than
devoting specific sections to these two items, which would lead to considerable double-wording, we
have deemed it more useful to discuss them in context as they arose. The term ‘issues for
Interpretation’ has been chosen to indicate that this step is related to the Interpretation phase.
Identification of issues for Interpretation helps create a checklist of all Goal and scope, Inventory and
Impact assessment issues of possible relevance for the Interpretation phase
The items procedures, reporting and issues for Interpretation are treated in the Inventory analysis and
the Impact assessment phases, in the same way as described above for Goal and scope definition.
Procedures and reporting are treated similarly in the Interpretation phase, too, but for obvious reasons
issues for Interpretation is then a superfluous item.
One remaining point is what the Scope definition step exactly comprises. It is not clear from the ISO
standards what should be stated about the issues and/or steps in the Scope definition and what in the
Inventory analysis and Impact assessment.
The suggestions provided by ISO 14040 and 14041 on Scope definition are slightly different. Under the
heading ‘scope of the study’ a list of items is given in ISO 14040 (1997E), clause 5.1.2 (and referred to
in ISO 14041, clause 5.3.1), which shall be considered and should be clearly described:
- the function of the system;
- the functional unit;
- the system to be studied;
- the system boundaries;
- allocation procedures;
- the types of impact and the methodology of Impact assessment and subsequent Interpretation to be
- data requirements;
- assumptions;
- limitations;
- the initial data quality requirements;
- the type of critical review, if any; and
- the type and format of the report required for the study.
We suggest that these elements of the ISO Scope definition be split into three clusters. The first of
these covers a number of basic choices for the entire study, including:
1 “Procedures” is a separate step in Part 2a - Guide - but not in Part 3 - Scientific background.
Part 3: Scientific background 48 May 2001
- temporal coverage (including infinite time horizon in modeling economic flows, environmental
interventions and impacts);
- geographical coverage;
- Technology coverage;
- coverage of economic processes (initial system boundaries);
- coverage of environmental interventions and impacts;
- mode of analysis1; and
- level of sophistication.
In this Guide these issues will be elaborated in the step ‘Scope of the study’.
The second cluster covers basic choices regarding function, functional unit, alternatives and reference
flows. Here, a separate step of Goal and scope definition is devoted to these key issues of an LCA
The third cluster comprises critical review and reporting, viz. of all the basic choices with respect to
functional unit, systems compared, Inventory analysis, Impact assessment and Interpretation. This so-
called Goal and Scope Report is drafted for the purpose of critical review and stakeholder comments
and, in comparison to ISO 14040 and 14041, is here extended to cover reporting on all the main choices
of all the methodological steps distinguished. For this reporting dimension, separate guidelines are given
in each step of the Goal and scope definition.
The relation between the steps of Goal and scope definition in this Guide and those derived from ISO
14041 is shown in Figure
1 “Mode of analysis” refers to a subject that is not (yet) treated in the ISO document but has become a key topic
in the LCA debate. It concerns the distinction between descriptive and change-oriented applications, also
known as the “marginal-average discussion” (cf. Udo de Haes and Wrisberg, 1997; Frischknecht, 1998). The
distinction between these two types of application appears to be extremely important, for two reasons:
1. it enables an explicit connection to be made with the application and hence with the Goal definition, the
functional unit, etc.;
2. it may have major consequences for methodological details during Inventory analysis, Impact assessment
and Interpretation.
As indicated above, this Guide focuses on change-oriented analysis for long-term structural decisions.