Quantifying system uncertainty of life cycle assessment based on Monte Carlo simulation

Background, aim, and scope

Many studies evaluate the results of applying different life cycle impact assessment (LCIA) methods to the same life cycle inventory (LCI) data and demonstrate that the assessment results would be different with different LICA methods used. Although the importance of uncertainty is recognized, most studies focus on individual stages of LCA, such as LCI and normalization and weighting stages of LCIA. However, an important question has not been answered in previous studies: Which part of the LCA processes will lead to the primary uncertainty? The understanding of the uncertainty contributions of each of the LCA components will facilitate the improvement of the credibility of LCA.

Methodology

A methodology is proposed to systematically analyze the uncertainties involved in the entire procedure of LCA. The Monte Carlo simulation is used to analyze the uncertainties associated with LCI, LCIA, and the normalization and weighting processes. Five LCIA methods are considered in this study, i.e., Eco-indicator 99, EDIP, EPS, IMPACT 2002+, and LIME. The uncertainty of the environmental performance for individual impact categories (e.g., global warming, ecotoxicity, acidification, eutrophication, photochemical smog, human health) is also calculated and compared. The LCA of municipal solid waste management strategies in Taiwan is used as a case study to illustrate the proposed methodology.

Results

The primary uncertainty source in the case study is the LCI stage under a given LCIA method. In comparison with various LCIA methods, EDIP has the highest uncertainty and Eco-indicator 99 the lowest uncertainty. Setting aside the uncertainty caused by LCI, the weighting step has higher uncertainty than the normalization step when Eco-indicator 99 is used. Comparing the uncertainty of various impact categories, the lowest is global warming, followed by eutrophication. Ecotoxicity, human health, and photochemical smog have higher uncertainty.

Discussion

In this case study of municipal waste management, it is confirmed that different LCIA methods would generate different assessment results. In other words, selection of LCIA methods is an important source of uncertainty. In this study, the impacts of human health, ecotoxicity, and photochemical smog can vary a lot when the uncertainties of LCI and LCIA procedures are considered. For the purpose of reducing the errors of impact estimation because of geographic differences, it is important to determine whether and which modifications of assessment of impact categories based on local conditions are necessary.

Conclusions

This study develops a methodology of systematically evaluating the uncertainties involved in the entire LCA procedure to identify the contributions of different assessment stages to the overall uncertainty. Which modifications of the assessment of impact categories are needed can be determined based on the comparison of uncertainty of impact categories.

Recommendations and perspectives

Such an assessment of the system uncertainty of LCA will facilitate the improvement of LCA. If the main source of uncertainty is the LCI stage, the researchers should focus on the data quality of the LCI data. If the primary source of uncertainty is the LCIA stage, direct application of LCIA to non-LCIA software developing nations should be avoided.     

Statistical analysis for the development of national average weighting factors—visualization of the variability between each individual’s environmental thoughts

Purpose  

Weighting is one of the steps involved in life cycle impact assessment (LCIA). This enables us to integrate various environmental impacts and facilitates the interpretation of environmental information. Many different weighting methodologies have already been proposed, and the results of many case studies with a single index have been published. However, a number of problems still remain. Weighting factors should be based on the preferences of society as a whole so that the life cycle assessment (LCA) practitioner can successfully apply them to every product and service. However, most existing studies do not really measure national averages but only the average of the responses obtained from the people actually sampled. Measuring the degree of uncertainty in LCIA factors is, therefore, one of the most important issues in current LCIA research, and some advanced LCIA methods have tried to deal with the problem of uncertainty. However, few weighting methods take into account the variability between each individual’s environmental thoughts. LIME2, the updated version of life cycle impact assessment method based on endpoint modeling (LIME), has been developed as part of the second LCA national project of Japan. One of the aims of LIME2 is to develop new weighting factors which fulfill the following requirements: (1) to accurately represent the environmental attitudes of the Japanese public, (2) to measure the variability between each individual’s environmental thoughts and reflect them in the choice of suitable weighting factors.     

The formulation of life cycle impact assessment framework for Malaysia using Eco-indicator

Background, aim, and scope  

Life Cycle Assessment (LCA) is an emerging supporting tool designed to help practitioner in systematically assessing the environmental performance of selected product’s life cycle. A product’s life cycle includes the extraction of raw materials, production, and usage, and ends with waste treatment or disposal. Life cycle impact assessment (LCIA) as a part of LCA is a method used to derive the environmental burdens from selected product’s stages. LCIA is structured in classification, characterization, normalization and weighting. Presently most of the LCIA practices use European database to establish the characterization, normalization and weighting value. However, using these values for local LCA practice might not be able to reflect the actual Malaysian’s environmental scenario. The aim of this study is to create a Malaysian version of normalization and weighting value using the pollution database within Malaysia.     

The Glasgow consensus on the delineation between pesticide emission inventory and impact assessment for LCA

Purpose

Pesticides are applied to agricultural fields to optimise crop yield and their global use is substantial. Their consideration in life cycle assessment (LCA) is affected by important inconsistencies between the emission inventory and impact assessment phases of LCA. A clear definition of the delineation between the product system model (life cycle inventory—LCI, technosphere) and the natural environment (life cycle impact assessment—LCIA, ecosphere) is missing and could be established via consensus building.

Methods

A workshop held in 2013 in Glasgow, UK, had the goal of establishing consensus and creating clear guidelines in the following topics: (1) boundary between emission inventory and impact characterisation model, (2) spatial dimensions and the time periods assumed for the application of substances to open agricultural fields or in greenhouses and (3) emissions to the natural environment and their potential impacts. More than 30 specialists in agrifood LCI, LCIA, risk assessment and ecotoxicology, representing industry, government and academia from 15 countries and four continents, met to discuss and reach consensus. The resulting guidelines target LCA practitioners, data (base) and characterisation method developers, and decision makers.

Results and discussion

The focus was on defining a clear interface between LCI and LCIA, capable of supporting any goal and scope requirements while avoiding double counting or exclusion of important emission flows/impacts. Consensus was reached accordingly on distinct sets of recommendations for LCI and LCIA, respectively, recommending, for example, that buffer zones should be considered as part of the crop production system and the change in yield be considered. While the spatial dimensions of the field were not fixed, the temporal boundary between dynamic LCI fate modelling and steady-state LCIA fate modelling needs to be defined.

Conclusions and recommendations

For pesticide application, the inventory should report pesticide identification, crop, mass applied per active ingredient, application method or formulation type, presence of buffer zones, location/country, application time before harvest and crop growth stage during application, adherence with Good Agricultural Practice, and whether the field is considered part of the technosphere or the ecosphere. Additionally, emission fractions to environmental media on-field and off-field should be reported. For LCIA, the directly concerned impact categories and a list of relevant fate and exposure processes were identified. Next steps were identified: (1) establishing default emission fractions to environmental media for integration into LCI databases and (2) interaction among impact model developers to extend current methods with new elements/processes mentioned in the recommendations.

     

Cradle-to-gate study of red clay for use in the ceramic industry

Background, Goal and Scope  The ceramic tile industry is one of the most important industries in Spain, with the highest concentration of firms to be found in the province of Castellón on the Mediterranean coast. The basic input material for this industry is red clay. The aim of this study was to carry out an LCA of the process of mining, treating and marketing this clay in order to identify the stages and unit processes that have the greatest impact on the environment. This LCA examines all the stages of the red clay from cradle to the customer’s gate, including the process of mining and treating the clay in the mining facilities and its later distribution to end users. Methods  Life cycle inventory (LCI): An exhaustive LCI was performed by collecting data from the mine run by Watts Blake Bearne Spain, S.A. (WBB-Spain) in Castellón. Inputs and outputs were collected for all the unit processes involved in the mining, treatment and marketing of the clay:

Ecological Toxicity Methods and Metals. An examination of two case studies (8 pp + 1)

Goal, Scope and Background The Apeldoorn Workshop (April 15th, 2004, Apeldoorn, NL) brought together specialists in LCA and Risk Assessment to discuss current practices and complications of the life cycle impact assessment (LCIA) ecological toxicity (ecotox) methodologies for metals. The consensus was that the LCIA methods currently available do not appropriately characterize impacts of metals due to lack of fundamental metals chemistry in the models. A review of five methods available to perform ecotox impact assessment for metals has been prepared to provide Life Cycle Assessment (LCA) practitioners with a better understanding of the current state of the science and potential biases related to metals. The intent is to provide awareness on issues related to ecotox impact assessment. Methods In this paper two case studies, one a copper based product (copper tube), the other a zinc-based product (gutter systems), were selected and examined by applying freshwater ecological toxicity impact models – USES-LCA, Eco-indicator 99 (EI 99), IMPACT 2002, EDIP 97, and CalTOX-ETP. Both studies are recent, comprehensive, cradle-to-gate, and peer-reviewed. The objective is to review the LCIA results in the context of the practical concerns identified by the Apeldoorn Declaration, in particular illustrating any inconsistencies such as chemical characterization coverage, species specificity, and relative contribution to impact results. Results and Discussion The results obtained from all five of the LCIA methods for the copper tube LCI pointed to the same substance as being the most important – copper. This result was obtained despite major fundamental differences between the LCIA methods applied. However, variations of results were found when examining the freshwater ecological toxicity potential of zinc gutter systems. Procedural difficulties and inconsistencies were observed. In part this was due to basic differences in model nomenclature and differences in coverage (IMPACT 2002+ and EDIP 97 contained characterization factors for aluminium that resulted in 90% and 22% contribution to burden respectively, the other three methods did not). Differences were also observed relative to the emissions source compartment. In the case of zinc, air emissions were found to be substantial for some ecotox models, whereas, water emissions results were found to be of issue for others. Conclusions This investigation illustrates the need to proceed with caution when applying LCIA ecotox methodologies to life cycle studies that include metals. Until further improvements are made, the deficiencies should be clearly communicated as part of LCIA reporting. Business or policy decisions should not without further discussion be based solely on the results of the currently available methods for assessing ecotoxicity in LCIA. Outlook The outlook to remedy deficiencies in the ecological toxicity methods is promising. Recently, the LCIA Toxic Impacts Task Force of the UNEP/SETAC Life Cycle Initiative has formed a subgroup to address specific issues and guide the work towards establishment of sound characterization factors for metals. Although some measure of precision of estimation of potential impact has been observed, such as in the case of copper, accuracy is also a major concern and should be addressed. Further investigation through controlled experimentation is needed, particularly LCIs composed of a variety of inorganics as well as organics constituents. Support for this activity has come from the scientific community and industry as well. Broader aspects of structure and nomenclature are being collectively addressed by the UNEP/SETAC Life Cycle Initiative. These efforts will bring practical solutions to issues of naming conventions and LCI to LCIA flow assignments.     

Notions on the Design and Use of an Ideal Regional or Global LCA Database

Goal, Scope and Background

More and more national and regional life cycle assessment (LCA) databases are being established satisfying the increasing demand on LCA in policy making (e.g. Integrated Product Policy, IPP) and in industry. In order to create harmonised datasets in such unified databases, a common understanding and common rules are required. This paper describes major requirements on the way towards an ideal national background LCA database in terms of co-operation, but also in terms of life cycle inventory analysis (LCI) and impact assessment (LCIA) methodology.

Methods

A classification of disputed methodological issues is made according to their consensus potential. In LCI, three main areas of dissent are identified where consensus seems hardly possible, namely system modelling (consequential versus attributional), allocation (including recycling) and reporting (transparency and progressiveness). In LCIA the time aspect is added to the well-known value judgements of the weighting step.

Results and Discussions

It is concluded that LCA methodology should rather allow for plurality than to urge harmonisation in any case. A series of questions is proposed to identify the most appropriate content of the LCA background database or the most appropriate LCI dataset. The questions help to identify the best suited approach in modelling the product system in general and multioutput and recycling processes in particular. They additionally help to clarify the position with regard to time preferences in LCIA. Intentionally, the answers to these questions are not attributed to particular goal and scope definitions, although some recommendations and clarifying explanations are provided.

Recommendations and Perspective

It is concluded that there is not one single ideal background database content. Value judgements are also present in LCI modelling and require pluralistic solutions; solutions possibly based on the same primary data. It is recommended to focus the methodological discussion on aspects where consensus is within reach, sensible and of added value for all parties.

     

In reply to hertwich & pease, Int. J. LCA 3 (4) 180 — 181, “ISO 14042 restricts use and development of impact assessment”

Life Cycle Impact Assessment describes indicators and does not predict actual impacts. The value of an LCA is its comprehensive review of all stages of a product’s life cycle and its synoptic view of all relevant environmental issues. The current version of the 14042 draft describes the uniqueness of Life Cycle Impact Assessment approach which is distinct from other assessment techniques. The wording was designed to help users of the standard understand how and why LCIA is distinct from other assessment methods. In closing, we would like to highlight our opinion that the present document on the level of a DIS is sound, stable and practical within the ISO 14040 series of standards. We do not agree withHertwich & Pease that the present document prevents the use of LCIA. It makes a choice regarding the exclusion of weighting across categories in order to prevent misuse in deriving inappropriate claims. And for characterisation it has achieved a well founded synthesis. In addition, we strongly believe that this standard will stimulate the international scientific discussion of LCA and will substantially contribute to enhanced and more valuable applications of LCA in the future.     

Impact assessment of abiotic resource consumption conceptual considerations

The impact assessment of the consumption of abiotic resources, such as fossil fuels or minerals, is usually part of the Life Cycle Impact Assessment (LCIA) in LCA studies. The problem with the consumption of such resources is their decreasing availability for future generations. In currently available LCA methods (e.g. Eco-indicator’ 99/Goedkoop and Spriensma 1999, CML/Guinée 2001), the consumption of various abiotic resources is aggregated into one summarizing indicator within the characterization phase of the LCIA. This neglects that many resources are used for different purposes and are not equivalent to each other. Therefore, the depletion of reserves of functionally non-equivalent resources should be treated as separate environmental problems, i.e. as separate impact sub-categories. Consequently, this study proposes assigning the consumption of abiotic resources to separate impact sub-categories and, if possible, integrating them into indicators only according to their primary function (e.g. coal, natural gas, oil → consumption of fossil fuels; phosphate rock → consumption of phosphate). Since this approach has been developed in the context of LCA studies on agricultural production systems, the impact assessment of the consumption of fossil fuels, phosphate rock, potash salt and lime is of particular interest and serves as an example. Following the general LCA framework (Consoli et al. 1993, ISO 1998), a normalization step is proposed separately for each of the subcategories. Finally, specific weighting factors have been calculated for the sub-categories based on the ’distance-to-target’ principle. The weighting step allows for further interpretation and enables the aggregation of the consumption of different abiotic resources to one summarizing indicator, called the Resource Depletion Index (RDI). The proposed method has been applied to a wheat production system in order to illustrate the conceptual considerations and to compare the approach to an established impact assessment method for abiotic resources (CML method, Guinée 2001).     

User needs analysis and development of priorities for life cycle impact assessment

The development of the LCIA programme of the UNEP/SETAC Life Cycle Initiative started with a global survey of LCA practitioners. There were 91 LCIA-specific responses from all global regions. Respondents gave an indication of how they use LCA with respect to both the stage of LCA that they base decisions on (LCI, LCIA or a combination of both) as well as the types of decisions which they support with LCA information. The issues requiring immediate attention within the UNEP SETAC Life Cycle Initiative identified from this User Needs analysis are the need for transparency in the methodology, for scientific confidence and for scientific co-operation as well as the development of a recommended set of factors and methodologies. Of interest is the fact that results from the different regions highlighted the need for different impact categories. Based on this information proposals were made for new impact categories to be included in LCA (and thus LCIA). The LCIA programme aims to enhance the availability of sound LCA data and methods and to deliver guidance on their use. More specifically, it aims to 1) make results and recommendations widely available for users through the creation of a worldwide accessible information system and 2) establish recommended characterisation factors and related methodologies for the different impact categories, possibly consisting of sets at both midpoint and damage level. The work of the LCIA programme of the UNEP/SETAC Life Cycle Initiative has been started within four task forces on 1) LCIA information system and framework, 2) natural resources and land use, 3) toxic impacts, and 4) transboundary impacts. All participants willing to contribute to these efforts are invited to contact the LCIA programme manager or to join the next LCIA workgroup meeting that will take place in at the world SETAC congress in Portland on Thursday 18 November 2004.     

45th Discussion forum on LCA—environmentally extended input–output analysis and LCA, September 15, 2011, Berne, Switzerland

The discussion forum on life cycle assessment (LCA) on September 15, 2011, aimed at summarizing recent environmentally extended input?Coutput analysis (EE-IOA) and the combination with LCA for the computation of environmental impact of imports. Input?Coutput tables (IOT) represent the financial flows in a country or economic regions. Extending IOT with information on emissions and resource uses allows for the analysis of environmental impacts due to production and consumption activities in a country. This instrument is called EE-IOA. It enables the analysis of total environmental impacts of countries or economic regions. The combination with trade statistics and LCA was presented as an alternative to multiregional input?Coutput models for determining environmental impacts of imports over the whole life cycle. The 45th LCA forum gathered several international speakers who provided a broad and qualified view on the topic. The theoretical background, results for different countries and regions, uncertainties, and possible improvement options for EE-IOA were discussed. The following main conclusions were drawn at the end of the discussion forum: EE-IOA is a useful instrument for analyzing the total environmental impacts of countries and the main drivers of environmental impacts. As a next important step, the participants would like to see an increase in user friendliness of EE-IOA combined with LCA, e.g., by harmonizing data, data formats, and classifications.     

Life cycle assessment of the selective catalytic reduction process for power plants

The overall reduction of the environmental impact by the use of selective catalytic reduction (SCR) of nitrogen oxide emissions in power plants was determined by strict application of ISO 14040 and ISO/DIS 14041. Special emphasis was placed on the implementation of the total product life cycle (PLC) of ammonium molybdate as a key input material. The environmental impact was generated by application of the life cycle assessment (LCA) concept of “ecoscarcity” and integrated in the life cycle inventory analysis (LCI) of SCR systems. The LCI was used to generate the life cycle impact assessment (LC1A) by use of different quantitative valuation methods. Under consideration of the overall LCIA results and the environmental protection costs of the SCR variants, the Ecological Effectiveness of the SCR alternatives was determined. The results enable plausible conclusions with regard to the ecological advantages of the use of deNOx catalysts in the SCR used in hard-coal fired power plants.     

Comparison between three different LCIA methods for aquatic ecotoxicity and a product environmental risk assessment

Background and Objective  In the OMNIITOX project 11 partners have the common objective to improve environmental management tools for the assessment of (eco)toxicological impacts. The detergent case study aims at: i) comparing three Procter &c Gamble laundry detergent forms (Regular Powder-RP, Compact Powder-CP and Compact Liquid-CL) regarding their potential impacts on aquatic ecotoxicity, ii) providing insights into the differences between various Life Cycle Impact Assessment (LCIA) methods with respect to data needs and results and iii) comparing the results from Life Cycle Assessment (LCA) with results from an Environmental Risk Assessment (ERA). Material and Methods  The LCIA has been conducted with EDIP97 (chronic aquatic ecotoxicity) [1], USES-LCA (freshwater and marine water aquatic ecotoxicity, sometimes referred to as CML2001) [2, 3] and IMPACT 2002 (covering freshwater aquatic ecotoxicity) [4]. The comparative product ERA is based on the EU Ecolabel approach for detergents [5] and EUSES [6], which is based on the Technical Guidance Document (TGD) of the EU on Environmental Risk Assessment (ERA) of chemicals [7]. Apart from the Eco-label approach, all calculations are based on the same set of physico-chemical and toxicological effect data to enable a better comparison of the methodological differences. For the same reason, the system boundaries were kept the same in all cases, focusing on emissions into water at the disposal stage. Results and Discussion  Significant differences between the LCIA methods with respect to data needs and results were identified. Most LCIA methods for freshwater ecotoxicity and the ERA see the compact and regular powders as similar, followed by compact liquid. IMPACT 2002 (for freshwater) suggests the liquid is equally as good as the compact powder, while the regular powder comes out worse by a factor of 2. USES-LCA for marine water shows a very different picture seeing the compact liquid as the clear winner over the powders, with the regular powder the least favourable option. Even the LCIA methods which result in die same product ranking, e.g. EDIP97 chronic aquatic ecotoxicity and USES-LCA freshwater ecotoxicity, significantly differ in terms of most contributing substances. Whereas, according to IMPACT 2002 and USES-LCA marine water, results are entirely dominated by inorganic substances, the other LCIA methods and the ERA assign a key role to surfactants. Deviating results are mainly due to differences in the fate and exposure modelling and, to a lesser extent, to differences in the toxicological effect calculations. Only IMPACT 2002 calculates the effects based on a mean value approach, whereas all other LCIA methods and the ERA tend to prefer a PNEC-based approach. In a comparative context like LCA the OMNIITOX project has taken the decision for a combined mean and PNEC-based approach, as it better represents the ‘average’ toxicity while still taking into account more sensitive species. However, the main reason for deviating results remains in the calculation of the residence time of emissions in the water compartments. Conclusion and Outlook  The situation that different LCIA methods result in different answers to the question concerning which detergent type is to be preferred regarding the impact category aquatic ecotoxicity is not satisfactory, unless explicit reasons for the differences are identifiable. This can hamper practical decision support, as LCA practitioners usually will not be in a position to choose the ’right’ LCIA method for their specific case. This puts a challenge to the entire OMNIITOX project to develop a method, which finds common ground regarding fate, exposure and effect modelling to overcome the current situa-tion of diverging results and to reflect most realistic conditions.     

Environmental assessment of future technologies: how to trim LCA to fit this goal?

Introduction

New and innovative technologies may claim substantial efficiency gains in the future. However, they are often assessed based on their current performance, measured in the laboratory or in pilot plants. The goal of discussion forum 38 was, on one hand, to shed light on the main drivers and principles that ensure a sensible and fair assessment of far future technologies. On the other hand, the most recent European developments in prospective technology assessment of emerging energy technologies and the related quantification of external costs were touched upon.

Discussion

The discussion forum started with three talks dedicated to external costs and multicriteria decisions presenting results of the New Energy Externality Developments for Sustainability project. After three presentations considering long-term LCI modeling aspects, lectures were held covering industry implementation and case studies. The following main conclusions were drawn at the end of discussion forum 38: (a) life cycle assessment (LCA) is considered a useful tool for environmental assessments of future energy technology, (b) consistency in LCA modeling of future situations is achieved by adapting data in the foreground (electricity-generating technology) and in the background (electricity supply mix, material manufacture, transport services, etc.), (c) external cost assessments and multicriteria decision analysis involve value judgments and thus do lead to a variety of different conclusions, (d) the present situation must be known properly to be able to model possible future situations, and (e) challenges are the data availability and definition of consistent scenarios of the future.     

No Matter – How?: Dealing with Matter‐less Stressors in LCA of Wind Energy Systems

The portfolio of impacts that are quantified in life cycle assessment (LCA) has grown to include rather different stressors than those that were the focus of early LCAs. Some of the newest life cycle impact assessment (LCIA) models are still in an early phase of development and have not yet been included in any LCA study. This is the case for sound emissions and noise impacts, which have been only recently modeled. Sound emissions are matter‐less, time dependent, and bound to the physical properties of waves. The way sound emissions and the relative noise impacts are modeled in LCA can show how new or existing matter‐less impacts can be addressed. In this study, we analyze, through the example of sound emissions, the specific features of a matter‐less impact that does not stem from the use of a kilogram of matter, nor is related to the emission of a kilogram of matter. We take as a case study the production of energy by means of wind turbines, contradicting the commonly held assumption that windmills have no emissions during use. We show how to account for sound emissions in the life cycle inventory phase of the life cycle of a wind turbine and then calculate the relative impacts using a noise LCIA model.     

Perceived uncertainties of characterization in LCA: a survey

Purpose

Uncertainty analyses in life cycle assessment (LCA) literature have focused primarily on the life cycle inventory (LCI) phase, but LCA experts generally agree that the life cycle impact assessment (LCIA) phase is likely to contribute even more to the overall uncertainty of an LCA result. The magnitude of perceived uncertainties in characterization relative to that in LCI, however, has not been examined in the literature. Here, we use the pedigree approach to gauge the perceived uncertainty in the characterization phase relative to the LCI phase. In addition, we evaluate the level of approval on the pedigree approach as a means to characterize uncertainty in LCA.

Methods

Applying the Numeral Unit Spread Assessment Pedigree (NUSAP) approach to environmental risk assessment literature, we extracted the criteria for evaluating the uncertainty in the characterization phase. We used expert elicitation to identify a pool of experts and conducted a survey, to which 47 LCA practitioners from 12 countries responded. In order to reduce personal biases in perceived geometric standard deviation (GSD) values, we used two reference questions on weight and life expectancy at birth for calibration.

Results

Nearly half (49%) of respondents expressed their approval to the pedigree matrix approach as a means of characterizing uncertainties in LCA, and responses were highly sensitive to the respondent’s familiarity with the pedigree matrix. For instance, respondents who are highly familiar with the pedigree matrix were more polarized, with 15% and 19% of them expressing either strong approval or strong disapproval, respectively. Respondents less familiar with the pedigree approach were generally more favorable to its use. Compared with LCI, variability in characterization factors was influenced more strongly by geographical correlation and reliability of the underlying model, which showed 11 to 16% larger average GSDs when compared with the comparable criteria for LCI. Conversely, temporal correlation criterion was a less significant factor in characterization than in LCI.

Conclusions and discussion

Overall, survey respondents viewed LCIA characterization as only marginally more uncertain than LCI, but with a wider variability in responses on characterization than LCI. This finding indicates the need for additional research to develop more thorough methods for characterizing uncertainties in life cycle impact assessment that are compatible with the uncertainty measures in LCI.

     

Ambiguities in decision-oriented Life Cycle Inventories The Role of mental models

If the complexity of real, socio-economic systems is acknowledged, life cycle inventory analysis (LCI) in life cycle assessment (LCA) cannot be considered as unambiguous, objective, and as an exclusively data and science based attribution of material and energy flows to a product. The paper thus suggests a set of criteria for LCI derived from different scientific disciplines, practice of product design and modelling characteristics of LCI and LCA. A product system with its respective LCI supporting the process of effective and efficient decision-making should ideally be: a) complete, operational, decomposable, non-redundant, minimal, and comparable; b) efficient, i.e., as simple, manageable, transparent, cheap, quick, but still as ‘adequate’ as possible under a functionalistic perspective which takes given economic constraints, material and market characteristics, and the goal and scope of the study into account; c) actor-based when reflecting the decision-makers’ action space, risk-level, values, and knowledge (i.e. mental model) in view of the management rules of sustainable development; d) as site- and case-specific as possible, i.e. uses as much site-specific information as possible. This rationale stresses the significance of considering both (i) material and energy flows within the technosphere with regard to the sustainable management rules; (ii) environmental consequences of the environmental interventions on ecosphere. Further, the marginal cost of collecting and computing more and better information about environmental impacts must not exceed the marginal benefits of information for the natural environment. The ratio of environmental benefits to the economic cost of the tool must be efficient compared to other investment options. As a conclusion, in comparative LCAs, the application of equal allocation procedures does not lead to LCA-results on which products made from different materials can be compared in an adequate way. Each product and material must be modelled according to its specific material and market characteristics as well as to its particular management rules for their sustainable use. A generic LCA-methodology including preferences on methodological options is not definable.     

German network on life cycle inventory data

Reliability of Life Cycle Assessment (LCA) results depends on the availability and quality of Life Cycle Inventory (LCI) data. In order to provide high-quality LCI data for background systems in LCA and to make it applicable to a wider range of fields, harmonization strategies for already existing datasets and databases are required. In view of the high significance of LCI data as a basis of major fields of action within a sustainability strategy, the German Helmholtz Association (HGF), under the leadership of the Forschungszentrum Karlsruhe (FZK) has taken up this issue in its research programme. In 2002, the FZK conducted a preliminary study on ‘Quality Assurance and User-oriented Supply of a Life Cycle Inventory Data’ funded by the Federal Ministry of Education and Research (BMBF). Within the framework of this study, a long-term concept for improving the scientific fundamentals and practical use of LCI data was developed in association with external experts. The focus is on establishing a permanent German ‘Network on Life Cycle Inventory Data’ which will serve as the German information and cooperation platform for all scientific and non-scientific actors in the field of life cycle analysis. This network will integrate expertise on LCA in Germany, harmonise methodology and data, and use the comprehensive expert panel as an efficient basis for further scientific development and practical use of LCA. At the same time, this network will serve as a platform for cooperation on an international level. Current developments address methodological definitions for the initial information infrastructure. As a novel element, user needs are differentiated in parallel according to the broad application fields of LCI-data from product declaration to process design. Case studies will be used to define tailored interfaces for the database, since different data quality levels will be encountered.     

Weighting in Life Cycle assessments in a global context

The option of weighting impact categories according to ISO 14042 on Life Cycle Impact Assessment (LCIA) is particularly difficult for global organizations, as they have to consider a wide range of values. The motivation for employing weighting is usually based on the desire to simplify LCIA output, especially in circumstances where product system tradeoffs occur. Looking globally at regional variations in legislation, consumer values, monetary valuation, existing weighting sets and expert opinions, no globally agreed upon weighting set is likely to be derived. This is due to both the inherent subjectivity of weighting and local variations in environmental imperatives. Hence, the authors recommend that LCIA quantitative weighting, especially those provided in pre-packaged software instruments, should not be employed. Admittedly, to use a spectrum of LCIA results for internal design decisions, some kind of tradeoff analysis has to be performed, especially if comparing competing design alternatives. However, this trade-off analysis should be done separately from the technical LCA study and should reflect values and visions of the global organization, as well as the circumstances of the targeted market, in a qualitative way. For any external communication, none of the quantitative weighting sets can be used.