1、ANSI/ISO 14042-2000AMERICAN NATIONAL STANDARDEnvironmental management Life cycle assessment Life cycle impact assessmentAMERICAN SOCIETY FOR QUALITYP.O. BOX 3005MILWAUKEE, WI 53201-3005ANSI/ISO 14042-2000AMERICAN NATIONAL STANDARDEnvironmental managementLife cycle assessment Life cycle impact assess
2、mentApproved as an American National Standard by:NSF International (NSF)American Society for Testing identification of theimpact categories, related category indicators and characterization models, category endpoints and theassociated LCI results that the LCA study will address. For example, the cli
3、mate change impact categoryrepresents emissions of greenhouse gases (LCI results) using infrared radiative forcing as the categoryindicator. See also Table 1.b) Assignment of LCI results (classification) to the impact categories.c) Calculation of category indicator results (characterization).The ind
4、icator results for different impact categories together represent the LCIA profile for the product system.Clause 5 describes in more detail the mandatory elements of LCIA mentioned above and in Figure 1, and providesspecific requirements.4.3.3 There are optional elements and information as listed be
5、low which can be used depending on the goal andscope of the LCA study.a) Calculating the magnitude of category indicator results relative to reference information (normal-ization).b) Grouping: sorting and possibly ranking of the impact categories.c) Weighting: converting and possibly aggregating ind
6、icator results across impact categories using numericalfactors based on value-choices.d) Data quality analysis: better understanding the reliability of the collection of indicator results, the LCIA profile.5 Mandatory elements5.1 GeneralFor the LCIA phase, the outcome of the mandatory elements is th
7、e collection of indicator results for the differentimpact categories.5.2 Concept of category indicatorsFigure 2 illustrates the concept of category indicators based on an environmental mechanism. Every impactcategory has its own environmental mechanism. The acidification impact category is used in F
8、igure 2 as anexample.Characterization models reflect the environmental mechanism by describing the relationship between the LCIresults, category indicators and in some cases category endpoint(s). The characterization model is used to derivethe characterization factors. For each impact category, the
9、necessary components includeGbe identification of the category endpoint(s),Gbe definition of the category indicator for given category endpoint(s),Gbe identification of appropriate LCI results that can be assigned to the impact category, taking into account thechosen category indicator and identifie
10、d category endpoint(s), andGbe identification of the characterization model and the characterization factors.ANSI/ISO 14042-20005This procedure facilitates the collection, assignment and characterization modelling of appropriate LCI results. Thisalso helps to highlight the scientific and technical v
11、alidity, assumptions, value-choices and degree of accuracy inthe characterization model.Figure 2 Concept of category indicatorsTable 1 provides examples of terms used in this International Standard. The environmental mechanism is the totalof environmental processes related to climate change.Table1Ex
12、ampleoftermsTerm ExampleImpact category Climate changeLCI results Greenhouse gasesCharacterization model IPCCamodelCategory indicator Infrared radiative forcing (W/m2)Characterization factor Global warming potential for each greenhouse gas(kg CO2-equivalents/kg gas)Indicator result kg of CO2-equival
13、entsCategory endpoints Coral reefs, forest, cropsEnvironmental reference Degree of linkage between category indicator and categoryendpointNOTE Further examples are provided in ISO/TR 14047 1.aIntergovernmental Panel on Climate Change.5.3 Selection of impact categories, category indicators and charac
14、terization models5.3.1 This subclause provides guidance and requirements for the selection of impact categories, categoryindicators and characterization models including the criteria for environmental relevance.For most LCA studies, existing impact categories, category indicators or characterization
15、 models will be selected.Whenever impact categories, category indicators and characterization models are selected in an LCA study, therelated information shall be referenced. The requirements and recommendations of this subclause apply to theANSI/ISO 14042-20006referenced information. However, in so
16、me cases existing impact categories, category indicators or characterizationmodels are not sufficient to fulfil the defined goal and scope of the LCA study, and new ones have to be defined.When new impact categories, category indicators or characterization models are defined, the requirements andrec
17、ommendations in this subclause also apply.The category indicator can be chosen anywhere along the environmental mechanism between the LCI results andthe category endpoint(s) (see Figure 2).5.3.2 The following requirements apply for the selection of impact categories, category indicators andcharacter
18、ization models:a) the selection of impact categories, category indicators and characterization models shall be consistent with thegoal and scope of the LCA study;b) the sources for impact categories, category indicators and characterization models shall be referenced;c) the selection of impact categ
19、ories, category indicators and characterization models shall be justified;d) accurate and descriptive names shall be provided for the impact categories and category indicators;e) the selection of impact categories shall reflect a comprehensive set of environmental issues related to theproduct system
20、 being studied, taking the goal and scope into consideration;f) the environmental mechanism and characterization model which relate the LCI results to the category indicatorand provide a basis for characterization factors shall be described;g) the appropriateness of the characterization model used f
21、or deriving the category indicator in the context of thegoal and scope of the study shall be described.5.3.3 In addition, the following recommendations apply for the selection of impact categories, category indicatorsand characterization models:a) the impact categories, category indicators and chara
22、cterization models should be internationally accepted, i.e.based on an international agreement or approved by a competent international body;b) the impact categories should represent the aggregated emissions or resource use of the product system onthe category endpoint(s) through the category indica
23、tors;c) value-choices and assumptions made during the selection of impact categories, category indicators andcharacterization models should be minimized;d) the impact categories, category indicators and characterization models should avoid double counting unlessrequired by the goal and scope definit
24、ion, for example when the study includes both human health andcarcinogenicity;e) the characterization model for each category indicator should be scientifically and technically valid, and basedupon a distinct identifiable environmental mechanism and/or reproducible empirical observation;f) the exten
25、t to which the characterization model and the characterization factors are scientifically and technicallyvalid should be identified;g) the category indicators should be environmentally relevant.5.3.4 Depending on the environmental mechanism and the goal and scope, spatial and temporal differentiatio
26、nof the characterization model relating the LCI results to the category indicator should be considered. The fate andtransport of the substances should be part of the characterization model.LCI results other than mass and energy flow data included in an LCA study, e.g. land use, shall be identified a
27、ndtheir relationship to corresponding category indicators shall be determined.ANSI/ISO 14042-200075.3.5 The environmental relevance of the category indicator or characterization model should be clearly stated interms of the following criteria:a) the ability of the category indicator to reflect the c
28、onsequences of the LCI results on the category endpoint(s),at least qualitatively;b) the addition of environmental data or information to the characterization model with respect to the categoryendpoint(s), includingGbe the condition of the category endpoint(s),Gbe the relative magnitude of the asses
29、sed change in the category endpoints,Gbe the spatial aspects, such as area and scale,Gbe the temporal aspects, such as duration, residence time, persistence, timing, etc.,Gbe the reversibility of the environmental mechanism, andGbe the uncertainty of the linkages between the characterization model a
30、nd the changes in the categoryendpoints.5.4 Assignment of LCI results (classification)This subclause provides guidance for assignment of LCI results to impact categories (often referred to asclassification).When LCI results are assigned to impact categories, environmental issues associated with the
31、LCI results can behighlighted.Assignment of LCI results to impact categories should consider the following, unless otherwise required by the goaland scope:Gbe assignment of LCI results which are exclusive to one impact category;Gbe identification of LCI results which relate to more than one impact c
32、ategory, includingGbe distinction between parallel mechanisms, e.g. SO2is allocated between the impact categories of humanhealth and acidification, andGbe allocation among serial mechanisms, e.g. NOxmay be assigned to both ground-level ozone formation andacidification.If LCI results are unavailable
33、or of insufficient data quality for the LCIA to achieve the goal and scope of the study,either an iterative data collection or an adjustment of the goal and scope is required.5.5 Calculation of category indicator results (characterization)This subclause provides guidance and requirements for calcula
34、tion of indicator results (often referred to ascharacterization). The calculation involves the conversion of LCI results to common units and the aggregation ofthe converted results within the impact category. This conversion uses characterization factors. The outcome of thecalculation is a numerical
35、 indicator result.The method of calculating indicator results shall be identified and documented, including the value-choices andassumptions used.The usefulness of the indicator results for a given goal and scope depends on the accuracy, validity andcharacteristics of the characterization models and
36、 characterization factors. The number and kind of simplifyingANSI/ISO 14042-20008assumptions and value-choices used in the characterization model for the category indicator also vary betweenimpact categories. A trade-off often exists between characterization model simplicity and accuracy. Variation
37、in thequality of category indicators among impact categories may influence the overall accuracy of the LCA study, forexampleGbe the complexity of the environmental mechanisms between the system boundary and the category endpoint,Gbe the spatial and temporal characteristics, for example the persisten
38、ce of a substance in the environment, andGbe the dose-response characteristics.Calculation of indicator results involves two steps:a) selection and use of characterization factors to convert the assigned LCI results to common units;b) aggregation of the converted LCI results into the indicator resul
39、t.One example of a category indicator is infrared radiative forcing. A characterization factor, in this case the globalwarming potential factor for each greenhouse gas, is used to calculate the converted LCI results for each gas inunits of carbon dioxide equivalents. Their contributions are then agg
40、regated into an indicator result in terms of totalcarbon dioxide equivalents.Additional data about the environmental condition can enhance the meaning and usability of the indicator results.This issue may also be dealt with in the data quality analysis.6 Optional elements6.1 GeneralThis clause descr
41、ibes three optional LCIA elements: normalization, grouping and weighting. These elements mayuse information from outside the LCIA framework. Such information should be justified and reported. Normalizationemploys baselines and/or reference information. Grouping and weighting employ value-choices.6.2
42、 Calculating the magnitude of the category indicator results relative to reference information(normalization)The aim of the normalization of indicator results is to better understand the relative magnitude for each indicatorresult of the product system under study. Calculating the magnitude of indic
43、ator results relative to referenceinformation (often referred to as normalization) is an optional element which may be helpful in, for exampleGbe checking for inconsistencies,Gbe providing and communicating information on the relative significance of the indicator results, andGbe preparing for addit
44、ional procedures, such as grouping, weighting or life cycle interpretation.This procedure transforms an indicator result by dividing it by a selected reference value. Some examples ofreference values areGbe the total emissions or resource use for a given area, which may be global, regional, national
45、 or local,Gbe the total emissions or resource use for a given area on a per capita basis or similar measurement, andGbe a baseline scenario, such as a given alternative product system.ANSI/ISO 14042-20009The selection of the reference system should consider the consistency of the spatial and tempora
46、l scales of theenvironmental mechanism and the reference value.The normalization of the indicator results changes the outcome of the mandatory elements of the LCIA phase. Itmay be desirable to use several reference systems to show the consequence on the outcome of mandatoryelements of the LCIA phase
47、. A sensitivity analysis may provide additional information about the choice ofreference. The collection of normalized indicator results represents a normalized LCIA profile.6.3 GroupingGrouping is assigning impact categories into one or more sets as predefined in the goal and scope definition, and
48、itmay involve sorting and/or ranking. Grouping is an optional element with two possible procedures:Gbe to sort the impact categories on a nominal basis, e.g. by characteristics such as emissions and resources orglobal regional and local spatial scales;Gbe to rank the impact categories in a given hie
49、rarchy, e.g. high, medium, and low priority.Ranking is based on value-choices.The application and use of grouping methods shall be consistent with the goal and scope of the LCA study and itshall be fully transparent.Different individuals, organizations, and societies may have different preferences, therefore it is possible thatdifferent parties will reach different ranking results based on the same indicator results or normalized indicatorresults.6.4 WeightingWeighting is the process of converting indicator results of different impact categories by using numerical factorsbased on valu
