SIST-TP ISO/TR 14047:2008

TECHNICAL ISO/TR
REPORT 14047
First edition
2003-10-01
Environmental management — Life cycle
impact assessment — Examples of
application of ISO 14042
Management environnemental — Évaluation de l'impact du cycle de
vie — Exemples d'application de l'ISO 14042

Reference number
©
ISO 2003
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ii © ISO 2003 — All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Abbreviated terms. 1
4 Organization of examples in ISO/TR 14047. 3
4.1 Mandatory and optional elements. 3
4.2 Scope of examples. 3
4.3 Organization of document and route map. 4
5 Elements of LCIA as illustrated in the examples.6
5.1 General. 6
5.2 Mandatory elements. 6
5.3 Optional elements (related to ISO 14042:2000, Clause 6). 15
6 Examples of the mandatory elements of LCIA . 17
6.1 General. 17
6.2 Example 1 — Use of two different materials for gas pipelines . 17
6.3 Example 2 – Two acidification impact category indicators. 24
6.4 Example 3 — Impacts of greenhouse gas (GHG) emissions and carbon sinks on forestry
activities. 29
6.5 Example 4 – Assessment of endpoint category indicators. 38
6.6 Example 5 – Choice of material for a wind spoiler in car design study . 45
7 Examples of the optional elements of LCIA.51
7.1 General. 51
7.2 Example 1 — Application of optional elements in ISO 14042:2000, 6.2 Calculating the
magnitude of the category indicator results relative to reference information
(normalization) . 51
7.3 Example 2 — Application of optional elements in ISO 14042:2000, 6.2 Calculating the
magnitude of the category indicator results relative to reference information
(normalization) . 52
7.4 Example 6 – Normalization of LCIA indicator results for the use of different refrigerator
gases in ISO 14042:2000, 6.2 Calculating the magnitude of the category indicator results
relative to reference information (normalization). . 54
7.5 Example 7 – Normalization in a waste management study using ISO 14042:2000, 6.2
Calculating the magnitude of the category indicator results relative to reference
information (normalization). 61
7.6 Example 1 — Application. 68
7.7 Example 5 — Application of ISO 14042:2000. 6.4 Weighting. 69
7.8 Example 8 – A technique for the determination of weighting factors using ISO 14042:2000,
6.4 Weighting. 70
7.9 Example 1 — Application. 75
7.10 Example 5 — Application of ISO 14042:2000, Clause 7 Data quality analysis . 77
7.11 Example 1 — Application. 78
Bibliography . 85

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no
longer valid or useful.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 14047 was prepared by Technical Committee ISO/TC 207, Environmental management,
Subcommittee SC 5, Life cycle assessment.
iv © ISO 2003 — All rights reserved

Introduction
The heightened awareness of the importance of environmental protection, and the possible environmental
1)
significance of a product system , has increased the interest in development of methods to better understand
this significance. One of the techniques being developed for this purpose is Life Cycle Assessment (LCA).
Life cycle impact assessment (LCIA) is the third phase of life cycle assessment, and its purpose is to assess a
product system's life cycle inventory analysis (LCI) results to better understand its environmental significance.
It models selected environmental issues called impact categories and, through the use of category indicators
which help condense and explain the LCI results, portrays the aggregate emissions or resources used for
each impact category to reflect their potential environment impacts.
This Technical Report provides examples to illustrate the application of ISO 14042, Environmental
management – Life cycle assessment — Life cycle impact assessment. It uses several examples concerning
key areas of ISO 14042 in order to enhance the understanding of its requirements.

1) In this Technical Report the term “product system” also includes service systems.
TECHNICAL REPORT ISO/TR 14047:2003(E)

Environmental management — Life cycle impact assessment —
Examples of application of ISO 14042
1 Scope
This Technical Report provides examples to illustrate current practice in carrying out a life cycle impact
assessment in accordance with ISO 14042. These are only examples of the total possible “ways” to satisfy the
provisions of ISO 14042. They reflect the key elements of the life cycle impact assessment (LCIA) phase of
the LCA.
NOTE The examples presented in this Technical Report are not exclusive; other examples exist to illustrate the
methodological issues described.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies. Members of ISO and IEC maintain registers of currently valid
International Standards.
ISO 14040:1997, Environmental management — Life cycle assessment — Principles and framework
ISO 14042:2000, Environmental management — Life cycle assessment — Life cycle impact assessment
3 Abbreviated terms
The following is a non-exhaustive list of abbreviated terms found in this Technical Report.
ADI allowable dose intake
AP acidification potential
CFC chlorofluorocarbon
CML Centre of Environmental Science, Leiden University
COD chemical oxygen demand
DALY disability-affected life years
DLY disability life years
E exponent
EBIR equal benefit incremental reactivity
EDIP environmental design of industrial products
EL environmental load
ELU environmental load unit
EPS environmental priorities strategy
ETP eco-toxicity potential
FU functional unit
GWP global warming potential
IIASA International Institute for Applied Systems Analysis
IPPC integrated pollution prevention and control
IPCC Intergovernmental Panel on Climate Change
LCA life cycle assessment
LCI life cycle inventory analysis
LCIA life cycle impact assessment
MDF medium density fibreroad
MIR maximum incremental reactivity
MOIR maximum ozone incremental reactivity
NP nutrification potential
ODP ozone depletion potential
OSB oriented standard board
PAH polycyclic aromatic hydrocarbon
PDF potentially disappeared fraction
PEC predicted environmental concentration
PNEC predicted no-effect concentration
POCP photochemical ozone creation potential
RIVM National Institute of Public Heath and the Environment
SE sensitive ecosystem category indicator
USES uniform system for the evaluation of substances
VOC volatile organic compound
WMO World Meteorological Organization
YLL years of life lost
2 © ISO 2003 — All rights reserved

4 Organization of examples in ISO/TR 14047
4.1 Mandatory and optional elements
The general framework of the LCIA phase is composed of several mandatory elements that convert Life Cycle
Inventory (LCI) results to indicator results. In addition, there are optional elements for normalizing, grouping or
weighting of the indicator results and data quality analysis techniques for assisting in the interpretation of the
results.
4.2 Scope of examples
The examples provided within this Technical Report illustrate and support the methodology specified in
Clauses 5, 6, 7 and 10 of ISO 14042:2000. The coverage is indicated in Table 1.
Table 1 — Elements or clauses of ISO 14042:2000 illustrated with examples
ISO 14042:2000 Example coverage in this Technical
IS0 14042 clause
reference Report
Clauses 1 to 4 Foreword, Scope, Normative references, Terms and Examples of impact categories
definitions, General description of LCIA
Clause 5 Mandatory elements Example 1, Example 2, Example 3,
Example 4, Example 5
5.1 General
5.2 Concept of category indicators
5.3 Selection of impact categories, category indicators
and characterization models
5.4 Assignment of LCI results (classification)
5.5 Calculation of category indicator results
(characterization)
Clause 6 Optional elements
6.1 General
6.2 Calculating the magnitude of the category indicator Example 1, Example 2, Example 6,
results relative to reference information Example 7
(normalization)
6.3
Grouping
6.4 Example 1
Weighting
Stem example, Example 5, Example 8
Clause 7 Data quality analysis Stem example, Example 5
Clause 8 Limitations of LCIA Not covered in ISO/TR 14047
Clause 9 Comparative assertions disclosed to the public
Clause 10 Reporting and critical review Example 1
In some key areas, more than one example is provided to illustrate the different ways in which it may be
possible to apply ISO 14042. It is important to stress this point. In many LCIA studies, more than one
approach or practice may be used which will still allow conformance with the methodology specified in
ISO 14042. There is currently no unique approach. This Technical Report may be thought of as illustrating a
number of ways that may be used in the LCIA phase as specified in ISO 14042. Table 2 gives the title of the
example and the purpose of the illustration.
Table 2 — Example titles and the purpose of the illustrations
Example ISO 14042:2000
Example title Purpose of illustration
No. subclause reference
1 Use of two different materials for gas Full procedure of LCIA 5.2 to 5.5, 6.2 to 6.4,
pipelines Clause 7 and (reference to
Clause 10)
2 Two acidification impact category Consequences of using general 5.3 to 5.5, Clause 6
indicators or site-dependent models
3 Impacts of greenhouse gas (GHG) GHG emissions and carbon sinks 5.2 to 5.5
emissions and carbon sinks on forestry
activities
4 Endpoint category indicators Transforming ionizing radiation 5.2 to 5.5
assessment inventory results into impact
category indicator (YLL)
5 Choice of material for a wind spoiler in Impact modelling at endpoint level 5.2 to 5.5, 6.4, Clause 7
car design study and weighting
6 Normalization of LCIA indicator results Normalization using different 6.2
for the use of different refrigerator types of reference information
gases
7 Normalization in a waste management Use of normalization in the 6.2 and (reference to
study communication processes Clause 10)
8 A technique for the determination of The use of a panel of experts in 6.4
weighting factors such a study
4.3 Organization of document and route map
This Technical Report is organized along the lines of a process “plant”. First, Clause 5 begins with a “General
description of LCIA” and introduces the examples. A central “stem” example, Example 1, runs through the
document illustrating the key areas between Clauses 5 to 10 of ISO 14042:2000. This uses one set of LCI
data and processes it through the LCIA stages. Examples illustrating the different paths possible within the
ISO 14042 methodology run in parallel to Example 1. These examples use different source data from
Example 1. Figure 1 presents the process in a flow diagram.
NOTE Following Clause 5 the examples are organized as follows:
Examples in Clause 6 are mandatory elements running consecutively, i.e. Example 1, Illustration of 5.2 to 5.5 of
ISO 14042:2000, followed by Example 2, followed by Example 3, and so on.
Examples in Clause 7 are organized on a “topic” basis, e.g. with all examples on Illustration of 6.2 of ISO 14042:2000 on
normalization, followed by examples on Illustration of 6.3 of ISO 14042:2000 on Grouping, and so on.
The reader may adopt a number of alternative ways of using this Technical Report. These are broadly as
follows:
 follow Example 1 from start to finish;
 select an alternative example and follow the process flow;
 select a topic and read all the alternative approaches on that particular topic.
Each example is preceded by an overview to describe the key area of ISO 14042 which will be illustrated. The
body of the example follows the overview. Where an example continues through the document, it generally
has not been necessary to precede each clause with an overview.
4 © ISO 2003 — All rights reserved

Figure 1 — Organization and route map for this Technical Report
5 Elements of LCIA as illustrated in the examples
5.1 General
This clause gives a general description of LCIA, explaining key elements of the procedure, and places the
examples in the context of ISO 14042:2000. The LCIA process elements are shown in Figure 2.

Figure 2 — Elements of the LCIA phase (ISO 14042:2000)
5.2 Mandatory elements
5.2.1 General
According to ISO 14042, the mandatory elements of LCIA are:
 selection of impact categories, category indicators and characterization models;
 assignment of LCI results (classification) to the impact categories;
 calculation of category indicator results (characterization ).
6 © ISO 2003 — All rights reserved

5.2.2 Selection of impact categories, category indicators and characterization models
5.2.2.1 General
For each impact category, a distinction can be made between LCI results, including extractions (inputs) and
emissions (outputs), category endpoints and intermediate variables in the environmental mechanism between
these two groups (sometimes called "midpoints"). This is illustrated in Figure 3.

Figure 3 — Concept of category indicators (Figure 2 from ISO 14042:2000)
When defining the impact categories, an indicator must be chosen somewhere in the environmental
mechanism. Often indicators are chosen at an intermediate level somewhere along that mechanism;
sometimes they are chosen at endpoint level. Table 3 shows examples of relevant intermediate variables and
relevant category endpoints for a number of impact categories.
Table 3 — Examples of intermediate variables and category endpoints for a number of impact
categories
Choices of indicator level
Impact category
Examples of intermediate variables Examples of category endpoints
Climate change Infrared radiation, temperature, sea-level Human life expectancy, coral reefs, natural
vegetation, forests, crops, buildings
Stratospheric UV-B radiation Human skin, ocean biodiversity, crops
ozone depletion
Acidification Proton release, pH, base-cation level, Al/Ca Biodiversity of forests, wood production, fish
ratio populations, materials
Nutrification Concentration of macronutrients (nitrogen, Biodiversity of terrestrial and aquatic ecosystems
phosphorus)
Human toxicity Concentration of toxic substances in Aspects of human health (organ functioning,
environment, human exposure human life expectancy, number of illness days)
Ecotoxicity Concentration or bio-availability of toxic Plant and animal species populations
substances in environment
In Tables 4, 5 and 6, LCI results and indicator results are expressed using the same functional unit (the one
selected in the LCI phase, Scope).
In Table 4, examples of terms used for defining an impact category and describing the chosen
characterization model are given for six different impact categories to further illustrate the principles of Table 1
from ISO 14042:2000. Impact Categories 1 and 2 are input-related; Impact Categories 3 to 6 are output-
related.
Table 4 — Examples of definitions and description of six impact categories
Term Impact Category 1 Impact Category 2
Impact category
Depletion of fossil energy resources Depletion of mineral resources,
(excluding energy resources)
LCI results Extraction of resources of different fossil Extraction of resources, expressed as
fuels useful material
Characterization model Cumulated energy demands Static scarcity model
Category indicator Energy content of energy resources Extraction of material in the ore as a
function of estimated supply horizon of
the reserve base
Characterization factor Low calorific value per mass unit Present extraction of the material in the
ore divided by estimated supply horizon
of the reserve base
Indicator result
Total low calorific value (megajoules) Total mass of used material in the ore
divided by estimated supply horizon of
the reserve base
Category endpoints Heating, mobility Availability of resources
Environmental relevance Diverse problems known from energy Diverse problems from mineral
crises resources
8 © ISO 2003 — All rights reserved

Table 4 (continued)
Term Impact Category 3 Impact Category 4
Impact category
Climate change Stratospheric ozone depletion
LCI results
Emissions of greenhouse gases Emissions of ozone-depleting gases
Category indicator Increase of infrared radiative forcing Increase of stratospheric ozone
(W/m ) breakdown
Characterization model
The model as developed by the IPCC Table 5 — The model as developed by
defining the global warming potential of the WMO defining the ozone depletion
different greenhouse gases potential for different ozone-depleting
gases
[6], [7]
[8], [9]
Characterization factor Global Warming Potential for time horizon Ozone Depletion Potential in the steady
of 100 years (GWP100) for each state (ODP ) for each emission
steady state
greenhouse gas emission (kg CFC-11-eq./kg emission)
(kg CO eq./kg emission)
Indicator result Kilograms of CO -equivalents Kilograms of CFC-11-equivalents
Category endpoints Years of life lost (YLL), coral reefs, crops, Illness days, marine productivity, crops
buildings
Environmental relevance
Infrared radiative forcing is a proxy for Empirical and experimental linkage
eventual effects on the climate, depending between UV-B radiation levels and
on the integrated atmospheric heat damage
absorption caused by emissions and the
distribution over time of the heat absorption
Term Impact Category 5 Impact Category 6
Impact category
Nutrification Ecotoxicity
LCI results Emissions of nutrients Emissions of organic substances to air,
water and soil
Category indicator
Deposition increase divided by N/P Predicted Environmental Concentration
equivalents in biomass increase divided by Predicted No-Effect
Concentration (PNEC)
Characterization model The stoichiometric procedure as described USES 2.0 model developed at RIVM,
by [10], which identifies the equivalence describing fate, exposure and effects of
between N and P for both terrestrial and toxic substances, adapted to LCA by
aquatic systems. [11]
Characterization factor
Nutrification Potential (NP) for each Ecotoxicity Potential (ETP) for each
eutrophicating emission to air, water and emission of a toxic substance to air,
soil water and soil
3–
(kg 1,4-dichlorobenzene eq./kg
(kg PO - eq./kg emission)
emission)
3–
Indicator result Kilograms of 1,4-dichlorobenzene
Kilograms of PO equivalents
equivalents
Category endpoints
Biodiversity, natural vegetation, algal bloom Biodiversity
Environmental relevance The nutrification indicator represents a The PNEC represents a threshold for a
clear causal factor in the mechanism of possible effect of the substance on the
nutrification for different types of species composition of an ecosystem;
ecosystems; it is defined at a global level no spatial differentiation is considered
In Table 4, all six examples use the category indicator at the level of intermediate parameters in the
environmental mechanism. In order to illustrate the number of possible options when defining an impact
category and choosing a characterization model, Table 5 gives examples of different category models and
category indicators within the environmental mechanism of one impact category – photochemical ozone
formation. The examples given are not the only alternatives. A similar table could be prepared for each of the
impact categories in Table 4. Five of the alternatives presented in Table 5 focus on the same category
indicator chosen early in the environmental mechanism, but compare five different characterizations models.
For the sixth alternative, the indicator is chosen close to the endpoint. The main distinguishing features are
presented in boldface type.
Table 5 — Example of terms and different characterization models for the impact category
photo-oxidant formation
Term Alternative 1 Alternative 2 Alternative 3
Impact category
Photo-oxidant formation Photo-oxidant formation Photo-oxidant formation
Emissions of substances Emissions of substances Emissions of substances
LCI results
(VOC, CO) to air (VOC, CO) to air (VOC, CO) to air
UNECE Trajectory model Maximum Incremental
Reactivity (MIR) scenario;
Characterization
Trajectory model [14]
Single-cell model [15], [16]
model
[12], [13]
Quantity of tropospheric ozone Quantity of tropospheric Quantity of tropospheric
Category indicator
formed ozone formed ozone formed
Photochemical Ozone Photochemical Ozone Kg ozone formed for each
Creation Potential (POCP) for Creation Potential (POCP) emission of VOC or CO to
each emission of VOC or CO for each emission of VOC air
Characterization
to air or CO to air
factor
(kg ethylene eq./kg emission) (kg ethylene eq./kg (kg ozone/kg emission)
emission)
Indicator result Kg ethylene equivalents Kg ethylene equivalents Kg ozone
Category endpoints Illness days, crops Illness days, crops Illness days, crops
Ozone formation estimated Ozone formation estimated Highest rise in ozone levels
with relatively high background with low background NO per added amount of
x
NO
Environmental standard VOC mixture, very
x
high NO concentration, high
relevance
x
concentration is inhibiting
ozone creation
10 © ISO 2003 — All rights reserved

Table 5 (continued)
Term Alternative 4 Alternative 5 Alternative 6
Photo-oxidant formation Photo-oxidant formation Photo-oxidant formation,
Impact category
impacts on vegetation
Emissions of substances Emissions of substances Emissions of substances
LCI results
(VOC, CO) to air (VOC, CO) to air (NO , VOC, CO) to air
x
Maximum Ozone Equal Benefit Incremental RAINS adapted to LCA
Incremental Reactivity Reactivity (EBIR) scenario; Option for spatial
(MOIR) scenario; Single-cell Single-cell model differentiation within
Characterization model
model Europe
[15], [16] [15], [16] [17]
Quantity of tropospheric Quantity of tropospheric Area of ecosystem times
ozone formed ozone formed duration and extent of
Category indicator
exposure above critical level
for plants
Kg ozone formed for each Kg ozone formed for each Extent of exposure above
emission of VOC or CO to emission of VOC or CO to critical level for each
air air emission of NO , VOC or
x
Characterization factor
CO to air
(kg ozone/kg emission) (kg ozone/kg emission)
(m ×××× ppm ×××× hours/kg
emission)
Indicator result Kg ozone Kg ozone
m × ppm × hours
Category endpoints Illness days, crops Illness days, crops Crops, natural vegetation
Highest ozone concentration NO and VOC contribute Includes the contribution from
x
per added amount of standard equally to ozone production, NO together with VOC and
x
VOC mixture, relatively high relatively low NO CO, permits spatial

x
Environmental NO concentration, realistic concentration, lower differentiation to take regional
x
relevance for peak situations concentrations of NO and differences in reactivity and
x
VOC both reduce ozone ecosystem sensitivity into
creation account. Models close to
endpoint
5.2.2.2 Identification of possible indicators
The task of LCIA is to establish a relation between the inputs, e.g. fossil fuels or minerals, and outputs of the
Life Cycle Inventory phase with the impacts on the environment. For this reason, for every impact category an
indicator shall be chosen in the environmental mechanism, which as far as possible represents the totality of
all impacts in the impact category. This indicator can in principle be located at any position in the mechanism,
from the LCI results down to the category indicators. In Table 6 this aspect is illustrated for an impact category
dealing with acidification. Here three different characterization models are compared, each of them focusing
on a distinct category indicator. The three models, and connected indicators, differ in their degree of
sophistication. The first category indicator is the simplest, and is defined at the level closest to the emissions.
The second category indicator is defined at the level of an intermediate variable close to the endpoint; while
the third indicator is defined at endpoint level, also known as damage approach. Again, the major
distinguishing cells are presented in boldface type.
Table 6 — Indicators and underlying models chosen at different places in the environmental
mechanism
Term Alternative examples for the category indicator for acidification
Impact category Acidification Acidification Acidification
Emissions of acidifying Emissions of acidifying Emissions of acidifying substances
LCI results
substances to air and substances to air to air
water
CML-method [10]; RAINS, adapted to LCA [11] Ecoindicator-99 [18], using the
and (Example 2 [6]) model Nature Planner [19];
Characterization
EDIP-model [17]
model
Fate modelling by SMART [20];
damage modelling by MOVE [16]
Maximum release of Deposition / Acidification Increase in PDF
vegetation
+
Category protons (H ) Critical Load
(Potentially Disappeared
indicator Fraction) of plant species in
natural areas
Acidification Potential (AP) Acidification Potential (AP) for Potentially Disappeared Fraction
for each acidifying each acidifying emission to air (PDF) for each acidifying emission
Characterization
emission to air and water to air
factor
(kg SO -eq./kg emission)
(kg SO -eq./kg emission)
(PDF⋅m ⋅yr/kg emission)
Kilograms SO equivalents Kilograms SO equivalents
Indicator result PDF⋅m ⋅yr
2 2
Biodiversity, natural Biodiversity, natural Biodiversity, natural vegetation,
Category
vegetation, wood, fish, vegetation, wood, fish, wood, fish, monuments
endpoints
monuments monuments
Maximum potential effect; Fate is included; risk of effects Fate and effects on natural
Environmental
fate is not included; no are spatially differentiated vegetation are included; effects in
relevance spatial differentiation the Netherlands are a proxy for
effects in Europe
Requirements for the selection of category indicators are described in 5.3 of ISO 14042:2000. These
requirements are addressed for the following indicators of the acidification impact category:
 maximum proton release indicator: very crude indicator, far removed from endpoints (i.e. little
environmental relevance), but easy to handle (pertains to all units mentioned);
 critical load indicator: spatially differentiated, relatively certain in the modelling, but closer to endpoints
(moderate environmental relevance in ISO terms);
 endpoint indicators: spatially differentiated, high environmental relevance in ISO terms, because at
endpoint level, but involving large uncertainties in the modelling up to the chosen endpoints.
5.2.2.3 Environmental relevance
The link between the LCI results (extractions, emissions and types of land use), and the category indicator is
normally given by clear modelling algorithms. The term environmental relevance refers to how much bearing
the category indicator has on the category endpoint it attempts to reflect in a general and qualitative way. This
helps understand the attributes and relevance of the impact category (see Figure 2). Typically, the
environmental relevance is higher for indicators chosen later in the environmental mechanism (see
ISO 14042:2000, 5.3.5).
For the example of acidification in Table 6, the following could be stated for the environmental relevance of the
indicator representing maximum proton release:
 ecosystems with their flora and fauna in temperate and subpolar zones are threatened by acidic
deposition;
12 © ISO 2003 — All rights reserved

 the intensity of the impact is closely related to the buffering capacity of the receiving soils and water
bodies. Low base-cation regions in Northern Europe and North America show a high intensity of impacts
due to acidification;
 acidification has a regional distribution with short-range and long-range impacts. Short range is related to
higher acid concentrations in air and part of the forest-decline effects, while the long-range impacts lead
to the breakdown of soil buffers and to the acidification of lakes and subsequent fish die-back;
 the duration of acidified environmental compartments is long, since only the weathering of base-cation-
containing rocks counteracts the effect;
 the reversibility of the impact depends on the category endpoint. By application of calcium carbonate or
lime to acidified soils, some vitality effects can be treated immediately while a reversibility for the loss of
natural species, for instance due to acidified lakes, is not given;
 a large number of research activities have been conducted and the mechanisms are quite well
understood.
In the majority of examples given throughout this Technical Report, the category indicator is chosen at the
level of an intermediate parameter in the environmental mechanism. Exceptions are Examples 4 and 5 where
indicators are chosen near the endpoint level for all impact categories. Example 2 illustrates the potential
importance of the location of the chosen indicator for the impact category acidification, comparing approaches
along the lines of the first two alternatives of Table 6.
5.2.2.4 Choice of impact categories
A list of commonly used impact categories is presented in Table 7.
[22]
Table 7 — Commonly used impact categories
Output-related categories:
 Climate change
 Stratospheric ozone depletion
 Photo-oxidant formation
 Acidification
 Nitrification
 Human toxicity
 Ecotoxicity
Input-related categories:
 Depletion of abiotic resources (e.g. fossil fuels, minerals)
 Depletion of biotic resources (e.g. wood, fish)
This list cannot be regarded as complete. Other categories may for instance focus on radiation, noise and
odour, working environmental impacts or land use, but for these categories as yet no widely accepted
characterization methods are available. In reference [22] to the table, land use was also included in the list of
commonly used impact categories.
The selection also depends on the definition of the system boundaries. For instance, solid waste can be
selected as a category. However, if the LCI results are specified in terms of the emission of single substances,
the waste flows are to be regarded as part of the product system and these flows have to be translated into
emissions related to other categories, as specified above. The same holds true for a possible “energy”
category.
Often, the characterization model is chosen among existing models; this is the case for the majority of
examples. Example 3 documents the development of a new impact category covering the sequestration of
carbon in a forestry-based product system, and Example 4 presents the principles behind impact categories
defined with indicators at endpoint level.
5.2.3 Assignment of LCI results (classification)
Assignment of LCI results to impact categories shows which results have an impact on which categories.
Often this information is provided by a table of characterization factors which come from the model chosen for
the impact category. A main distinction in ISO 14042 concerns the difference between serial and parallel
processes. The characteristic to remember in parallel processes is that one substance that has an impact on
different categories may have to be divided over these categories because one part of the emission leads to
effects in one category, and another part to effects in another category. For example, the emission of SO
contributes to three categories: acidification, climate change (counteracting) and human toxicity (see Figure 4).

Figure 4 — Example of parallel processes
Serial processes are illustrated for CFC emissions. The characteristic to remember in serial processes is that
a substance may consecutively contribute to different impact categories, again necessitating a choice
concerning the contribution to these consecutive categories. The emission of CFCs contributes to the
following two impact categories: first to climate change at tropospheric level, then to stratospheric ozone
depletion (see Figure 5).
Figure 5 — Example of a serial process
As stated above, for parallel processes the emissions should in principle be divided between the different
processes; for serial processes the same substance can in principle be attributed in its full amount to the
different types of impact, one after the other. It should be noted, however, that if characterization is based on
multimedia modelling, this attribution is taken into account automatically. Then classification is not an element
in itself.
14 © ISO 2003 — All rights reserved

In Example 1, the handling of parallel and serial impacts is discussed in the illustration of 5.4 of
ISO 14042:2000.
5.2.4 Calculation of category indicator results (characterization)
Following the identification of impact categories, the choice of indicators and selection or development of
characterization model, and the assignment of LCI results to impact categories, indicator values are then
calculated for each impact category using characterization factors. The procedure is illustrated in Examples 1,
2, 3, 4 and 5. Examples 1 and 3 illustrate characterization for impact categories defined early or at an
intermediate level in the environmental mechanism. Example 2 illustrates the use of spatially differentiated
characterization factors, while Examples 4 and 5 demonstrate characterization performed at endpoint level.
5.3 Optional elements (related to ISO 14042:2000, Clause 6)
5.3.1 General
Following the mandatory elements described above, there are a number of optional elements that may be
used to help explain the results of the LCA according to the goal definition of the study.
In ISO 14042, the optional elements are
 calculating the magnitude of category indicator results relative to reference information (normalization),
 grouping: sorting and possibly ranking of the impact categories,
 weighting: converting and possibly aggregating indicator results across impact categories using numerical
factors based on value choices,
 data quality analysis: better understanding the reliability of the collection of indicator results, i.e. the LCIA
profile.
5.3.2 Calculating the magnitude of category indicator results relative to reference information
(normalization)
ISO 14042 states:
“The aim of the normalization of indicator results is to better understand the relative magnitude of each
indicator result of the product system under study. Calculating the magnitude of indicator results relative to
reference information (often referred to as normalization) is an optional element, which may be helpful in, for
example
 checking for inconsistencies,
 providing and communicating information on the relative significance of the indicator results, and
 preparing for additional procedures, such as grouping, weighting or life cycle interpretation.”
Examples 1, 2, 6 and 7 show how normalization can be used to assist the interpretation of the environmental
profile and illustrate the significance of different choices of a normalization reference.
5.3.3 Grouping: sorting and ranking of the impact categories
Following normalization, grouping may be performed on the indicator results. Two types of grouping can be
carried out: sorting (which is descriptive) and ranking (which is normative). In general, both types of grouping
of the indicator results lead to better possibilities for interpretation of these results.
Sorting of the indicator scores may for example be done according to the
 spatial scale of the impact category (global, regional local),
 area of protection for the impact category (human health, natural environment, resources),
 degree that the impact category model is science- or value-choice-based.
Ranking of the indicator scores might apply criteria such as
 the degree of reversibility of the impacts,
 the degree of certainty of the impacts,
 policy priorities regarding the types of impact.
Example 1 illustrates sorting and ranking.
5.3.4 Weighting
For certain applications, a weighting process may be performed. This is understood as the conversion of
category indicator results by using numerical factors based on value choices. In con
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