Reinout Heijungs

Recent developments in Life Cycle Assessment.

Life Cycle Assessment is a tool to assess the environmental impacts and resources used throughout a products life cycle, i.e., from raw material acquisition, via production and use phases, to waste management. The methodological development in LCA has been strong, and LCA is broadly applied in practice. The aim of this paper is to provide a review of recent developments of LCA methods. The focus is on some areas where there has been an intense methodological development during the last years. We also highlight some of the emerging issues. In relation to the Goal and Scope definition we especially discuss the distinction between attributional and consequential LCA. For the Inventory Analysis, this distinction is relevant when discussing system boundaries, data collection, and allocation. Also highlighted are developments concerning databases and Input-Output and hybrid LCA. In the sections on Life Cycle Impact Assessment we discuss the characteristics of the modelling as well as some recent developments for specific impact categories and weighting. In relation to the Interpretation the focus is on uncertainty analysis. Finally, we discuss recent developments in relation to some of the strengths and weaknesses of LCA.

Life Cycle Assessment: Past, Present, and Future†

Environmental life cycle assessment (LCA) has developed fast over the last three decades. Whereas LCA developed from merely energy analysis to a comprehensive environmental burden analysis in the 1970s, full-fledged life cycle impact assessment and life cycle costing models were introduced in the 1980s and 1990 s, and social-LCA and particularly consequential LCA gained ground in the first decade of the 21st century. Many of the more recent developments were initiated to broaden traditional environmental LCA to a more comprehensive Life Cycle Sustainability Analysis (LCSA). Recently, a framework for LCSA was suggested linking life cycle sustainability questions to knowledge needed for addressing them, identifying available knowledge and related models, knowledge gaps, and defining research programs to fill these gaps. LCA is evolving into LCSA, which is a transdisciplinary integration framework of models rather than a model in itself. LCSA works with a plethora of disciplinary models and guides selecting the proper ones, given a specific sustainability question. Structuring, selecting, and making the plethora of disciplinary models practically available in relation to different types of life cycle sustainability questions is the main challenge.

Identifying best existing practice for characterization modeling in life cycle impact assessment

PurposeLife cycle impact assessment (LCIA) is a field of active development. The last decade has seen prolific publication of new impact assessment methods covering many different impact categories and providing characterization factors that often deviate from each other for the same substance and impact. The LCA standard ISO 14044 is rather general and unspecific in its requirements and offers little help to the LCA practitioner who needs to make a choice. With the aim to identify the best among existing characterization models and provide recommendations to the LCA practitioner, a study was performed for the Joint Research Centre of the European Commission (JRC).MethodsExisting LCIA methods were collected and their individual characterization models identified at both midpoint and endpoint levels and supplemented with other environmental models of potential use for LCIA. No new developments of characterization models or factors were done in the project. From a total of 156 models, 91 were short listed as possible candidates for a recommendation within their impact category. Criteria were developed for analyzing the models within each impact category. The criteria addressed both scientific qualities and stakeholder acceptance. The criteria were reviewed by external experts and stakeholders and applied in a comprehensive analysis of the short-listed characterization models (the total number of criteria varied between 35 and 50 per impact category). For each impact category, the analysis concluded with identification of the best among the existing characterization models. If the identified model was of sufficient quality, it was recommended by the JRC. Analysis and recommendation process involved hearing of both scientific experts and stakeholders.Results and recommendationsRecommendations were developed for 14 impact categories at midpoint level, and among these recommendations, three were classified as “satisfactory” while ten were “in need of some improvements” and one was so weak that it has “to be applied with caution.” For some of the impact categories, the classification of the recommended model varied with the type of substance. At endpoint level, recommendations were only found relevant for three impact categories. For the rest, the quality of the existing methods was too weak, and the methods that came out best in the analysis were classified as “interim,” i.e., not recommended by the JRC but suitable to provide an initial basis for further development.Discussion, conclusions, and outlookThe level of characterization modeling at midpoint level has improved considerably over the last decade and now also considers important aspects like geographical differentiation and combination of midpoint and endpoint characterization, although the latter is in clear need for further development. With the realization of the potential importance of geographical differentiation comes the need for characterization models that are able to produce characterization factors that are representative for different continents and still support aggregation of impact scores over the whole life cycle. For the impact categories human toxicity and ecotoxicity, we are now able to recommend a model, but the number of chemical substances in common use is so high that there is a need to address the substance data shortage and calculate characterization factors for many new substances. Another unresolved issue is the need for quantitative information about the uncertainties that accompany the characterization factors. This is still only adequately addressed for one or two impact categories at midpoint, and this should be a focus point in future research. The dynamic character of LCIA research means that what is best practice will change quickly in time. The characterization methods presented in this paper represent what was best practice in 2008–2009.

The LCIA midpoint-damage framework of the UNEP/SETAC life cycle initiative

Background, Aims and ScopeLife Cycle Impact Assessment (LCIA) methods can be grouped into two families: classical methods determining impact category indicators at an intermediate position of the impact pathways (e.g. ozone depletion potentials) and damage-oriented methods aiming at more easily interpretable results in the form of damage indicators at the level of the ultimate societal concern (e.g. human health damage). The Life Cycle Initiative, a joint project between UNEP1 and SETAC2, proposes a comprehensive LCA framework to combine these families of methods. The new framework takes a world-wide perspective, so that LCA will progress towards a tool meeting the needs of both developing and developed countries. By a more precise and broadly agreed description of main framework elements, the Life Cycle Initiative expects to provide a common basis for the further development of mutually consistent impact assessment methods.Main FeaturesInputs to the LCIA midpoint-damage framework are results of Life Cycle Inventory analyses (LCI). Impact pathways connect the LCI results to the midpoint impact categories with the corresponding indicators, as well as to the damage categories at the level of damages to human health, natural environment, natural resources and man-made environment, via damage indicators. Mid-point impact categories simplify the quantification of these impact pathways where various types of emissions or extractions can be aggregated due to their comparable impact mechanisms. Depending on the available scientific information, impact pathways may be further described up to the level of damage categories by quantitative models, observed pathways or merely by qualitative statements. In the latter case, quantitative modelling may stop at mid-point. A given type of emission may exert damaging effects on multiple damage categories, so that a corresponding number of impact pathways is required. Correspondingly, a given damage category may be affected jointly by various types of emissions or extractions. It is therefore an important task of the Life Cycle Initiative to carefully select damage indicators. The content of the midpoint and of the damage categories is clearly defined, and proposals are made on how to express the extent of environmental damage by suitable indicator quantities.Conclusions and OutlookThe present framework will offer the practitioner the choice to use either midpoint or damage indicators, depending on modelling uncertainty and increase in results interpretability. Due to the collaboration of acknowledged specialists in environmental processes and LCIA around the globe, it is expected that - after a few years of effort - the task forces of the Life Cycle Initiative will provide consistent and operational sets of methods and factors for LCIA in the future.

Three Strategies to Overcome the Limitations of Life‐Cycle Assessment

Summary Many research efforts aim at an extension of life-cycle assessment (LCA) in order to increase its spatial or temporal detail or to enlarge its scope. This is an important contribution to industrial ecology as a scientific discipline, but from the application viewpoint other options are available to obtain more detailed information, or to obtain information over a broader range of impacts in a life-cycle perspective. This article discusses three different strategies to reach these aims: (1) extension of LCA—one consistent model; (2) use of a toolbox—separate models used in combination; and (3) hybrid analysis—combination of models with data flows between them. Extension of LCA offers the most consistent solution. Developments in LCA are moving toward greater spatial detail and temporal resolution and the inclusion of social issues. Creating a supertool with too many data and resource requirements is, however, a risk. Moreover, a number of social issues are not easily modeled in relation to a functional unit. The development of a toolbox offers the most flexibility regarding spatial and temporal information and regarding the inclusion of other types of impacts. The rigid structure of LCA no longer sets limits; every aspect can be dealt with according to the logic of the relevant tool. The results lack consistency, however, preventing further formal integration. The third strategy, hybrid analysis, takes up an intermediate position between the other two. This strategy is more flexible than extension of LCA and more consistent than a toolbox. Hybrid analysis thus has the potential to combine the strong points of the other two strategies. It offers an interesting path for further discovery, broader than the already well-known combination of process-LCA and input-output-LCA. We present a number of examples of hybrid analysis to illustrate the potentials of this strategy. Developments in the field of a toolbox or of hybrid analysis may become fully consistent with LCA, and then in fact become part of the first solution, extension of LCA.

Economic Allocation : Examples and Derived Decision Tree

Goal, Scope and BackgroundIn the recently published (Dutch) Handbook on LCA, economic allocation is advised as baseline method for most allocation situations in a detailed LCA. Although the Handbook on LCA aimed to provide a ‘cookbook’ with operational guidelines for conducting each step of an LCA, this was not completely achieved for the allocation step. The guidelines for allocation largely remained at the level of principles. This restricted elaboration of economic allocation may hamper application in practice. Therefore, this paper elaborates some examples applying economic allocation.MethodTwo concepts are of particular importance when applying economic allocation: functional flow and multi-functional process. The definitions of these concepts are presented and discussed. The basic principle of economic allocation is that having determined the various functional flows of a multi-functional process, all other flows need to be allocated to these functional flows according to their shares in the total proceeds. Proceeds are based on prices and these are not always easy to determine for a process. A summary of possible solutions for different problems when determining prices is given.Results and DiscussionThe examples presented focus on co-production and various recycling situations. All examples are hypothetical in order to avoid discussions on the data. The examples show that the prices of the functional flows determine the allocation results. It is of importance to have correct information on the relative prices of the functional flows at stake, especially whether they are negative or positive. Learning from these examples, we establish a decision tree for economic allocation. The decision tree is meant for identifying and handling multi-functionality situations starting from a defined (product) system. This decision tree is with minor adaptations also applicable to other allocation methods and has a more general value than for the economic allocation method only.Conclusions and perspectiveThe examples have helped us to establish a decision tree for handling the multi-functionality problem by economic allocation. The examples can be broadened to other materials and allocation situations. We would encourage others to provide other examples and experiences as we expect that these will help to further improve and refine the guidelines and decision tree for economic allocation in future.

Identification of key issues for further investigation in improving the reliability of life-cycle assessments

The interative nature of life-cycle assessment (LCA) means that more details are looked for until a certain level of reliability has been achieved. This paper is concerned with the identification of key issues for further investigation in such an iterative procedure. Key issues in this context are defined as those aspects of an LCA which need more detailed research to arrive at a solid conclusion. The main concept in the context of finding key issues is the study of the propagation of uncertainties in underlying data. The structured procedure of LCA can be described in mathematical terms, so that standard mathematical techniques for the study of the propagation of uncertainties can be employed. The influence of uncertainties in input data on uncertainties in output data can be calculated, and the main source of the resulting uncertainties can be identified. The result of the analysis is a list of prioritized key issues for more detailed research and more accurate data.

Material flows and economic models: an analytical comparison of SFA, LCA and partial equilibrium models

Abstract The growing concern for environmental problems in the current economy has spurred the study of the way materials and substances flow through the economy, resulting in many different types of analysis. Since all of these have their merits and shortcomings, much of the present theoretical research seems to be focusing on combining the best aspects of each model type into an integrated model. The aim of this paper is to make a first step in bridging the gap between the various types of analysis of material flows in the economy, by discussing the main differences and similarities of three often employed model types: substance flow analysis, life cycle assessment and partial economic equilibrium analysis. Instead of submitting each model to a lengthy theoretical discussion, we apply them to a single, hypothetical example of a pollution problem. By doing so we are able to evaluate the differences and similarities of the methods and results of the model in a practical way. It appears that the results of the three models are complementary rather than contradictory. Each of them puts an emphasis on different aspects of ‘the real world’. A sequential application of a number of limited models may therefore be an approach that provides more useful information than the tedious construction and application of an encompassing model that integrates these models.

A generic method for the identification of options for cleaner products

Life cycle assessment, a method for the assessment of the environmental impacts of products, is briefly explained. A mathematical method to perform the calculations and to identify dominant aspects in the environmental load of a product is developed. The results are used to derive expressions for a marginal analysis which can be used for improvement analysis. In this way, a designer or process engineer can determine which processes or materials to consider first when (re)designing a product. The method developed can also be used to estimate the reliability of the determination of the environmental load of the products analyzed in terms of the reliability of the data of the processes involved.

A proposal for the classification of toxic substances within the framework of life cycle assessment of products

Quantitative life cycle assessment (lca) is a method allocating the environmental impacts of the whole life cycle of a product to the functioning of that product. The scientific basis of the method is still being elaborated. In this paper a proposal is made to improve the scientific basis of one specific step of the methods: the aggregation of potentially toxic emissions of substances in one score for human toxicity and two scores for ecotoxicity. The aggregation is based on multimedia environmental models of Mackay simulating the behaviour of substances in the environment, and on toxicity data such as acceptable resp. tolerable daily intake (adi resp. tdi) and no observed effect concentration (noec) per substance. It is proposed to apply models describing the environmental fate of toxic substances in lcas of products. In addition, it is proposed to adopt the concept of a reference substance, as used in the ozone depletion potential (odp) and the global warming potential (gwp), to assess and aggregate emissions of potentially toxic substances.