Heijungs, Reinout

Hellweg, Stefanie

Huijbregts, Mark

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Conference Reports 22nd Biannual Meeting of iEMSs The second group dealt with the consequences for LCIA methods due to temporally differentiated weighting. First, impact categories were identified where impacts occur over a long time horizon: land use, global warming, ozone deple- tion, metal toxicity, acidification. Relevant future scenarios and dynamic models are required to account for a changing environment in a consistent way. The question as to whether or not one is able to perform long-term assessments was confirmed, although it was admitted that uncertainty in- creases with the extension of the time frame. No solution was ready on the table on how to assess this increased un- certainty. Finally, the group found no fundamental reasons to completely exclude long-term impacts from LCI. The third group discussed the consequences of a temporally differentiated weighting for the LCI modeling. The group saw no need for a more detailed isaggregation in time than the differentiation between short-term and long-term made in ecoinvent. If a further differentiation were needed, its reso- lution would need to be higher for the near future as com- pared to the resolution required for the far distant future (e.g., 10, 20, 50, 100, 200, 500, 1000 years). The group suggested allocating research resources to a spatial differen- tiation rather than to a further differentiation i time. The ecoinvent landfill model and fate models used in the impact assessment partly cover the same mechanisms, but have pri- marily been developed independently. A harmonization of the two models seems to be due. In the final discussion, it once again became apparent that there was no consensus concerning how future emissions should be included in impact assessment. There was agree- ment that long-term impacts hould be included in LCA and that long-term emissions hould be reported separately from the short-term emissions. There was no consensus on whether short-term and long-term impacts should be weighted equally. Some prefer to weigh short-term emissions higher because it is closer to them. Consistent and approved fore- casts should be used when modeling future changes in the environment in LCI and LCIA. The elevated uncertainty in emission factors of pollutants released uring thousands of years and the elevated uncertainty in the fate and damage analysis of such far future emissions were acknowledged. However, no ready-made solution was presented on how to include uncertainty in impact assessment. The presentations of the Discussion Forum and background information are available on the Internet <http://www.texma. orgfLCA-Forum/lca-forum.html>. On this webpage, there is also more information about the Discussion Forum se- ries, as well as an announcement of the coming events. References [1] ecoinvent Centre (2004): ecoinvent data v1.1, Final reports ecoinvent 2000 No. 1-15. CD-ROM, ISBN 3-905594-38-2, D0bendorf, CH: Swiss Centre for Life Cycle Inventories [2] Goedkoop Met al. (1999): The Eco-indicator 99: A Damage Ori- ented Method for Life Cycle Impact Assessment. Methodology Re- port, Amersfoort: Prd Consultants [3] Huijbregts MAJ, Guin~e JB, Reijnders L (2001): Priority Assess- ment of Toxic Substances in the Frame of LCA. II1: Export of Po- tential Impact over Time and Space. Chemosphere 44:59-65 [4] Doka G (2003): Life Cycle Inventories of Waste Treatment Serv- ices. CD-ROM, Final report ecoinvent 2000 No. 13, D0bendorf, CH: EMPA St. Gallen, Swiss Centre for Life Cycle Inventories [5] Huijbregts MAJ (1999): Priority Assessment of Toxic Substances in the Frame of LCA - The Multi-Media Fate, Exposure and Effect Model USES-LCA. Amsterdam: University of Amsterdam (NL) Conference Reports: 2nd Biannual Meeting of iEMSs Complexity and Integrated Resource Management: Uncertainty in LCA Osnabr(ick, Germany, June 14-17, 2004 Mark Huijbregts 1, Reinout Heijungs 2and Stefanie Hellweg 3I Department of Environmental Studies, University of Nijmegen, Nijmegen, The Netherlands (M.Hui!bregts@sci.kun.nl~ 2 Institute of Environmental Sciences, Leiden University, Leiden, The Netherlands (heiiunus@cml.leidenuniv.nl) 3 Institute of Chemical- and Bioengineering, Swiss Federal Institute of Technology, HCI, CH-8093 Zurich, Switzerland (hellweg @ chem.ethz.ch) The International Environmental Modelling and Software Society organised the second international iEMSs Conference, held June 14-17 2004 in OsnabrQck. The conference included research contributions from environmental modellers and software developers and users from a wide variety of disciplines, including the field of Life Cycle Assessment. Special emphasis was given to the analysis and modelling of complex human-technology-environment systems and the implications of complexity and uncertainty for management concepts and decision making. In this context, a session on 'Uncertainty in LCA' was organised focussing on tools to treat different ypes of uncertainty in an LCA decision- making context. All papers can be accessed through httD://www.iemss.orQ/iemss2004/ Reinout Heijungs (Leiden University) started the session with a review of approaches to treat uncertainty in LCA. The review discussed the typology of uncertainty that may be encountered in LCA, the qualitative and quantitative t ch- niques that are available to address these uncertainties, the inclusion of these techniques in LCA software tools, the (graphical) possibilities to show uncertainty in LCA out- comes, ways to simplify the uncertainty analysis, the inclu- sion of uncertainty analyses in case studies and (the difficul- ties in) the interpretation of uncertainty information. Philippa Notten (University of Cape Town) reported three graphical options to interpret output samples from quanti- tative uncertainty analyses. The results were from case stud- ies within the coal-fired power generation sector. It was found that box and whisker plots are good at representing the rela- Int J LCA 9 (5) 341 - 342 (2004) 9 ecomed publishers, D-86899 Landsberg, Germany and Ft. Worth/TX 9 Tokyo 9 Mumbai 9 Seoul 9 Melbourne 9 Paris 341 22nd Biannual Meeting of iEMSs Conference Reports tive importance of empirical parameter uncertainty and the uncertainty arising from the choice of decision variables, and show the degree of shifting between the options as well as the full range over which the options potentially act. Prin- cipal component analysis is considered particularly valuable to provide an overview of the results, where it is able to clearly present any trade-offs that have to be made between selection criteria, and the 'spread' of the options under con- sideration over the decision space. Lauren Basson (University of Cape Town) presented an ap- proach for the integrated consideration of both technical and valuation uncertainties during decision making supported by LCA-type environmental performance information. The inte- grated approach for the management of uncertainty is dem- onstrated for a technology selection decision for the recom- missioning of a coal-based power station. Distinguishability analysis howed that it was not possible to obtain a conclu- sive answer with regard to the preferred technology, due to the extensive uncertainty in the LCA-based environmental performance information. Principal component analysis of the ranking of the design scenarios demonstrated that valuation uncertainties had the most significant effect on the ranking of the design scenarios. The results suggest that stakeholder in- volvement is important, and that the 'encoding' of value judge- ments and preferences into LCA are to be avoided. Ralph Rosenbaum (EPFL Lausanne) presented an approach for estimating uncertainties for toxicological impact char- acterisation i  LCA. He proposed combining uncertainties estimated for intermediate r sults from the chemical fate, human intake fraction, and toxicological effects. Results were presented for impact contributions in the contexts of aquatic ecosystems and human health. The approach presented istransparent and easily applicable in practice to combine the uncertainty of the emission inventory with those of the im- pact assessment phase in a life cycle assessment s udy. Claudine Basset-Mens (INRA, France) presented a case study looking at'uncertainty and variability in an LCA of pig farm- ing systems, focussing on aquatic eutrophication. The quanti- fication of uncertainty ook into account the variation in tech- nical performance, mission factors, and the influence of the functional unit. For various farming systems, variability was investigated through differentiating by the production mode and farmer practices. For natural systems, variability due to physical and climatic haracteristics of catchments, that modi- fies nitrate fate, was explored. For the eutrophication impact category, the variability of field emissions and the choice of the functional unit was influential. Concerning inter-system variability, differences in farmer practices had a larger effect on eutrophication than differences between production modes. Finally, the physical characteristics of the catchment and the climate strongly affected the eutrophication result. Raquel Ferret (TEKNIKER, Spain) discussed the influence of agricultural data uncertainty in an LCA of biodegradable hydraulic lubricants. She found that fertilization practices and machinery operations in the agricultural step in the bio- degradable hydraulic lubricant production has the main en- vironmental impact. A Monte Carlo simulation has been performed showing that the eutrophication score is domi- nantly affected by input data uncertainty. Stefanie HeUweg (ETH Ziirich) presented an LCA on two plant-growth regulators considering various sources of un- certainty. These uncertainties were expressed as probability distributions and assessed via Monte-Carlo Simulation. The results howed that differences in median impact scores of a factor of 1.6 were sufficient in the impact categories of glo- bal warming, acidification, and eutrophication for a signifi- cant distinction of the products. By contrast, dispersions are large concerning the toxicity impact categories and the photooxidant creation potential. The implications of these uncertainties on the decision-making process were discussed and tentative rules of thumb for estimating the significance of results were put forward. In the Platform discussion, uncertainties in the weighting between various impact categories were named as a poten- tially relevant uncertainty. Involvement of stakeholders could be one solution to this problem. Aggregating LCIA methods include the danger of hiding uncertainties, although some methods consider different weighting schemes, e.g. accord- ing to cultural theory. An alternative approach could be the open illustration of the tradeoffs involved, such as presented in the talk of Basson. The question was also posed as to whether probability functions of LCI and LCIA flows are trustworthy. It was stated that more case studies are needed to learn about he shape of distribution functions and about the importance of different ypes of uncertainty and vari- ability in LCA. Meanwhile, the application of different prob- ability functions for uncertain parameters may be a prag- matic solution to address this uncertainty. It was concluded that uncertainties in LCA are typically large. There was con- cern that LCA becomes a meaningless tool because results may often be insignificant. Additionally, background proc- esses may frequently dominate the uncertainties of the fore- ground system, especially if generic uncertainty factors are used that are 'on the safe side'. One comment to this prob- lem was that the level of significance needs to be determined within the context in which the decision is made. In general, large confidence intervals of 90% or higher are applied. These high levels of significance may be suitable, e.g. if large monetary investments are a consequence of a decision. How- ever, in some situations, a smaller level of significance (e.g. 75%) may be sufficient, for instance if two products are compared that perform equally with respect o other crite- ria, such as price and performance. Another possibility to deal with high uncertainties i  to identify the parameters with the highest contribution to variance and try to reduce their uncertainty. In some cases, other solutions to reduce uncertainty may also be found (e.g. the re-definition of the functional unit). In any case, it was stressed by several par- ticipants that one should acknowledge that the aim of un- certainty analysis is not to take away uncertainty, and even not to reduce it. Its ultimate aim is to accommodate uncer- tainty in the decision-making procedure by giving it an ap- propriate place. There are various possibilities to do this, ranging from specifying confidence intervals to using uncer- tainty as a separate decision criterion. It was also stated that we may just have to accept hat LCA cannot always give a clear decision-recommendation due to the uncertainties in- volved, but that it may rather be used to understand the problems and tradeoffs involved in a decision. 342 Int J LCA 9 (5) 2004 

Complexity and integrated resource management: uncertainty in LCA

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Complexity and integrated resource management: uncertainty in LCA

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