Environmental Project, 995 – Update on Impact Categories, Normalisation and Weighting in LCA - Selected EDIP97-data

Update on Impact Categories, Normalisation and Weighting in LCA

Summary and conclusions

The report addresses a number of elements that all are related to the impact assessment step in the EDIP methodology:

- It gives a short introduction to some of the key elements in EDIP, e.g. the person equivalent, and the normalisation and weighting steps

- It gives a short discussion regarding choice of impact categories in relation to the recommendations in the ISO 14040 standard series, the international consensus regarding the applicability of different methods and the possibilities of performing calculations in the LCV programme that has been made especially in order to make EDIP calculations

- It describes a number of procedures that makes it possible to establish normalisation factors for the EU-15 and the World through extrapolation from relatively limited data sets

- It gives a detailed insight into the data base that has been used in the updating of the existing normalisation and weighting factors and to establish new factors for EU-15 and globally.

Regarding the choice of impact categories the report gives an overview of the categories that have been addressed in central LCA documents and method papers. A number of impact categories and the methods used for their assessment is common to all methods, while methods suggested for assessment of impacts on the local scale like human toxicity, ecotoxicity, noise, land use, etc. show marked differences in their approach. The report does not give a final recommendation whether a specific impact category shall be included in the LCA or whether one or the other approach is better. The recommendation is to include a sufficiently wide range of impact categories to fulfil the goal and scope of the LCA. Omission of impact categories should be a conscious and motivated choice, for which the lack of quantifiability for a given category is not necessarily a valid excuse. There are no requirements in the general LCA concept that all results should be quantified, and qualitative assessments can therefore be used to describe areas and issues that would otherwise be neglected. In some cases it will be relevant to develop and apply new methods in order to assess other impact categories than those traditionally addressed in LCA. This can be very demanding in terms of resources, and the final decision to do so should be determined by the commissioner and the LCA practician.

Another aim of the subproject was to develop new normalisation references for the current 15 member states of the EU (EU-15) and at the Global level – a "World Proxy". The background for this aim is that in the original EDIP method, normalisation references have only been developed for "Denmark" which can make it difficult to interpret the results of a LCA with a broader geographic scope. With the calculation of additional normalisation references, primarily for the EU-15, the LCA practitioner therefore gets better possibilities to assess the relative importance of different impact categories in an international perspective.

For the EU-15 the new normalisation references for photochemical ozone formation, acidification, nutrient enrichment, human toxicity and ecotoxicity were calculated by using different approaches and information from a broad range of literature sources. For some combinations of impact categories/compounds/activities, e.g. regarding many of the contributions to human toxicity and ecotoxicity, the normalisation references were calculated by extrapolation from selected national inventories as no consistent database was available. The extrapolation was based on the assumption that there is a linear relationship between the economic activity in a given EU-country and its emissions of a given substance or group of substances. Where possible, a cross reference was made with the few available data in order to give an indication of the uncertainty introduced by extrapolation.

The extrapolation approach used for calculation of global normalisation references was to use the relation between the economic activity in a country/region (measured as the Gross Domestic Product, GDP) and the emission of substances contributing to acidification. Both parameters have a well-founded statistical base for many countries and the correlation between them was considered to be adequate for further calculations. Based on the relationship a general extrapolation was developed, simply scaling the European normalisation reference to the global level, the so-called World Proxy.

The report describes the uncertainties associated with the newly developed normalisation references and recommends that the European normalisation references be used in general to calculate the base case scenarios. The recommendations are described in more detail in the Guidelines from the project, but are primarily based on the assumption that most LCA's include impact potentials that are found on a broad geographical scale and therefore should be matched by relevant normalisation factors. A final recommendation, however, is to use Danish normalisations references and the World Proxies in a sensitivity analysis in order to get a better indication of the robustness of the results.

The report gives a detailed insight into the data sources and calculation procedures that have been used in the calculation of each normalisation reference. For each impact category the database is presented in tabular form along with the most important intermediate calculations. This content is probably most interesting for experts in different areas, giving the possibility for other types of calculation, but is of course also a good starting point for future updates.

The last chapter in the report presents new weighting factors for Denmark, EU-15 and the World. This chapter also provides a detailed insight into the basic data, the way the weighting factors have been calculated, and the associated uncertainties. It is emphasized that the Global weighting factors for impact categories on the regional scale can only be calculated with a relatively high uncertainty, and for the impact categories on the local scale it has not been possible to establish reliable weighting factors. In order to make such calculations, information on current emissions as well as reduction targets must be available for each country/region. It was far beyond the scope of the project to collect and manipulate this very large amount of information, and it is therefore recommended to use the weighting factors for EU-15 in the base case calculations. It is, however, mentioned that especially the weighting factors for local impacts tend to be underestimated, compared to those for the regional impacts. The reason for this is that even for the EU-15 is it difficult to establish the full overview of the single member states' reduction targets for emissions of single substances or groups of substances.

It is concluded that the results of the project increases the possibility of making a LCA with a broader perspective than the original EDIP method allows. The broader perspective is, however, achieved at the cost of an increased uncertainty and the recommendations of the report and and the associated Guidelines are therefore focused on the use of sensitivity analysis to the extent relevant to fulfil the goal and scope of the study.