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Update on Impact Categories, Normalisation and Weighting in LCA 1 Introduction to the project
This report updates and extends the LCA normalisation and weighing data and methods that are presented in EDIP (Environmental Design of Industrial Products) (Wenzel et al. 1997; Hauchild & Wenzel 1998) further. Normalisation is a methodology used to compare results (e.g. potential greenhouse effect) to well-known figures and weighting aims to weight or rank different impact categories by using different principles i.e. political goals etc. The fundamental principles in normalisation and weighting are described in details in Wenzel et al. (1997). This project has had four goals through a consensus process to:
1.1 BackgroundThe background for the project is the international standards as well as the theoretical and practical considerations in Wenzel et al. (1997) and Haucshild and Wenzel (1998). The relevant sections from the relevant standards will shortly be introduced below. 1.1.1 The ISO standards of LCA and LCIAThe ISO 14040 standard "Life Cycle Assessment – Principles and frameworks" presents, as a part of an interactive process, the following steps in a Life Cycle Assessment:
The goal of an LCA study shall unambiguously state the intended application, the reasons for carrying out the study and the intended audience, i.e. to whom the results of the study are intended to be communicated (for details see ISO 14041 (ISO 1998)).
The phase of the life cycle inventory analysis involves the compilation and quantification of inputs and outputs, for a given product system throughout its life cycle (for details see ISO 14041 (ISO 1998)).
The phase of life cycle impact assessment is aimed at understanding and evaluating the magnitude and significance of the potential environmental impacts of a product system (for details see ISO 14042 (ISO 2000a)).
The phase of Life Cycle interpretation is where the findings of either the inventory analysis or the impact assessment, or both, are combined consistent with the defined goal and scope in order to reach conclusions and recommendations (for details see ISO 14043 (ISO 2000b)). The goal and scope definition, the inventory and the interpretation is mandatory while impact assessment is optional. According to ISO 14042 (ISO 2000a), life cycle impact assessment includes several steps from the Inventory to the Interpretation:
In Life Cycle Impact Assessment, the first three steps; assignment of inventory results to impact categories, the characterisation, and the classification are mandatory, while normalisation, grouping and weighting are optional elements. 1.2 The basis of normalisation and weighting in EDIP -methodologyIn EDIP as well as in the ISO standards, the overall advantage of normalisation is an increased possibility of interpretation of indicator results compared to each other. Further, it also provides an option of control by unveiling extreme indicator results. Finally, normalisation is a preparatory element in the optional element of weighting. The goal of normalisation is to set a common reference enabling comparison of different environmental impacts. It is an integral part of EDIP that the impacts are summarised for the area, which actually contributes to the current condition of the environment as it is experienced. For the global impacts it makes no difference where the environmental exchanges occur. But for regional and local impacts, only the exchanges occurring within the regions or local areas in question contribute to the current and future condition in the environment there. Due to this reasoning the normalisation and the subsequent weighting should ideally be carried out with normalisation references and weighting factors which, for each individual emission, are representative of the region where the emissions occur. However in the EDIP 1997, the data of the global impacts are available while data for regional impacts, generally, are not available. Instead, EDIP use Danish normalisation references as default values. In contrast to EDIP 97 it has been chosen to regard human toxicity and ecotoxicity as being primarily regional impacts with the same normalisation reference being applied to all EU-15 countries. It is, however, also possible to use the updated Danish normalisation reference, e.g. in an assessment of specific Danish products or product systems, or as an element in the sensitivity analysis. The same possibility also exists for most of the other EU-15 countries. Due to lack of data no regional normalisation references for other regions e.g. Central Africa and the Middle East have been developed. For acidification, normalisation references are provided for EU-15 as well as for the individual countries within EU-15. The individual normalisation references can be found in the current report. This project has provided a large number of normalisation references for EU-15 countries but some additional work still remains to be done before the ultimate goal, i.e. normalisation references for all relevant regions in the World, can be reached. A different approach has been taken in a parallel project within the LCA methodology and consensus project, site-characterisation (Hauschild & Potting, 2003). The present report does not discuss the pros and cons of either method, but provides only an update of the original EDIP97 method with respect to normalisation and weighting. 1.2.1 The person-equivalentThe global impact will always be much greater than the impact from a particular region, irrespective of the type of effect to which the impact contributes. Use of global impacts as the normalisation reference for the global impact categories and regional impacts for the regional and the local impact categories will thus give an imbalance in the normalisation, and it will result in global impacts from the product system coming to appear much less than the other impacts, because they are compared with the activity of the population of the entire world, while the others are compared only with the activity of e.g. the Danish population. To correct this bias and ensure that the set of normalising references constitutes a common scale for all impact categories, irrespective of whether they are global or regional, the normalisation references are calculated as the background impact over the course of one year per person in the area for which the impact is computed. This gives the normalisation references the unit "impact potential per person per year" for each individual impact category. 1.2.2 Establishing of normalisation referencesNormalisation references are established for Denmark, Europe (EU-15), and worldwide. For the relevant areas surveys of emissions contributing to the different impact categories have been established. The normalisation references are calculated based on EDIP (Wenzel et al. 1997):
where: mi is emitted quantity of substance i i.e. for each of the substances contributing to the impact category, the emitted quantity is multiplied with the equivalence factor for the specific substance giving the potential impact caused by the specific substance. The potential impacts by all the contributing substances are summarised and finally divided with the number of capita in the considered area. The figures used for normalisation in the EDIP methodology are the potential effects caused per capita in a defined geographical area e.g. potential greenhouse effect per capita per year. 1994 has been chosen as reference year. The actual normalisation references are expressed as kg CO2-eq./capita/year. The potential environmental impact e.g. greenhouse effect is expressed as person equivalents (PE) i.e. relative to the yearly contribution to the greenhouse effect by one person. In principle, the normalisation methodology allows different impact categories to be compared to each other. The present study develops normalisation references for Denmark, Europe (EU-15) and worldwide. 1.2.3 WeightingThe figures used for weighting in the EDIP methodology are the political reduction goals for the individual substances contributing to the relevant impact category. 2004 has been chosen as the reference year. The actual weighting factors are dimensionless. The weighting factors are linked to the above mentioned normalisation references with regard to the geographical area covered. The present study presents weighting factors for Denmark, Europe (EU-15) and worldwide. 1.2.4 Reference yearIn EDIP 1996, 1990 was used as reference year for normalisation, while 1990 and 2000 were chosen as reference years for weighting. In this update, 1994 and 2004 have been chosen as new reference years for normalisation references and weighting factors, respectively. The reason for choosing 1994 as reference year has been easy availability of compilations of data for most of the countries included in the EU-15 normalisation reference. In the recent years the availability of emission data has increased significantly e.g. by access to databases via Internet, and the delay caused by central compilation of data can be expected to be reduced in the future. Therefore, future updating can be expected to be faster with reference years closer to the actual year. 1.3 Guide to the readerThe report is divided in three parts. The first part deals with choice of impact categories and of normalisation reference. The second part is focused on update and expansion of selected impact categories, and the third part is dealing with update on weighting factors. Part I includes chapter 2 and chapter 3. Chapter 2 is an overview of five international lists regarding different impact categories. Each impact category is discussed and it is concluded whether the impact category is internationally recognised as well as to which extend characterisation models are agreed upon. Chapter 3 deals with a global approximation ("world proxies") of normalisation references. This includes the development of a simple extrapolation model based on emissions of acidifying substances. This allows the calculation of world proxies of the regional impact e.g. photochemical ozone formation and acidification as well as local impact i.e. human toxicity. Part II includes the update and expansion of impact categories. Each chapter describes shortly the impact category and includes a list of substances contributing to the impact. The methodology used for calculation of the normalisation reference and the calculated normalisation references for the whole world, EU-15 and Denmark are presented in each chapter. For each chapter, one or more appendices elaborates the content, e.g. by describing relevant data sources and providing detailed figures for emissions of substances in a number of countries. Chapter 4 deals with global warming. Global warming is a global impact category. Chapter 5 deals with stratospheric ozone depletion. Stratospheric ozone depletion is a global impact category. Chapter 6 deals with photochemical ozone formation, Photochemical ozone formation is considered primarily as a regional impact category. Normalisation references for EU-15 as well as Denmark are presented. Also a world proxy is presented. Chapter 7 deals with acidification. Acidification is considered as a regional impact category. A normalisation reference for EU-15 is provided as well as normalisation references for the individual countries within EU-15. A world proxy is presented. Chapter 8 deals with nutrient enrichment (eutrophication). Nutrient enrichment is considered as a local as well as a regional impact category. Normalisation references for Denmark as well as for EU-15 are provided. A world proxy is presented. Chapter 9 deals with human toxicity. Human toxicity is a local impact category. The chapter offers a normalisation reference for Denmark together with normalisation references for each of the EU-15 countries as well. A world proxy is also presented. Chapter 10 deals with ecotoxicity. Ecotoxicity is considered to be a local as well as regional impact category. Normalisation references for Denmark and EU are provided in the chapter. Further, normalisation references for each of the individual EU-15 countries is presented along with a world proxy. Part III includes chapter 11. It presents weighting factors for the seven impact categories The actual normalisation references and weighting factors are presented in tables in the summary in each chapter. The description of data collection, data handling, data sources, and data quality is intended for future update of the figures. The actual weighting factors are also presented in a summarising table. 1.4 ReferencesHauschild, M. & Wenzel, H. 1998, Environmental Assessment of Products. Volume 2 - Scientific background. First edition. Chapman & Hall, London. ISO 1997, Environmental management – Life cycle assessment – Principles and Framework. ISO 14040. ISO 1998, Environmental management – Life cycle assessment – Goal and scope definition and inventory analysis. ISO 14041. ISO 2000a, Environmental management – Life cycle assessment – Life cycle impact assessment. ISO 14042. ISO 2000b, Environmental management – Life cycle assessment – Life cycle interpretation. ISO 14043. Wenzel, H., Hauschild, M. & Alting, L. 1997, Environmental Assessment of Products. Volume 1 - Methodology, Tools and Case Studies in Product Development. First edition. Chapman & Hall, London.
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