Weighting in Practice:Implications for the Use of Life-Cycle Assessment in Decision Making

This article investigates how environmental trade-offs are handled in life-cycle assessment (LCA) studies in some Nordic companies. Through interviews, the use and understanding of weighting methods in decision making was studied. The analysis shows that the decision makers require methods with which to aggregate and help interpret the complex information from life-cycle inventories. They agreed that it was not their own values that should be reflected in such methods, but they were found to have different opinions concerning the value basis that should be used. The analysis also investigates the difficulties arising from using such methods. The decision makers seemed to give a broader meaning to the term weighting, and were more concerned with the comparison between environmental and other aspects than the weighting of different environmental impacts. A conclusion is that decision makers need to be more involved in modeling and interpretation. The role of the analyst should be to interpret the information needs of the decision maker, and help him or her make methodological choices that are consistent with these needs and relevant from his or her point of view. To achieve this, it is important that decision makers do not view LCA as a highly standardized calculation tool, but as a flexible process of collecting, organizing, and interpreting environmental information. Such an approach to LCA increases the chances that the results will be regarded as relevant and useful.     

Evaluating Land-Use Impacts: Selection of Surface Area Metrics for Life-Cycle Assessment of Mining

Land use is an increasingly important component of sustainability evaluations, and numerous performance metrics have evolved to meet this need. The selection of appropriate land-use metrics for decision makers, however, remains an ongoing challenge. Additionally, life-cycle practitioners often struggle to provide meaningful impact assessment because of challenges associated with traditional land-use impact metrics. This article is intended to assist decision makers and life-cycle practitioners who wish to more effectively measure and evaluate one aspect of land use: surface area occupation. Existing performance metrics are discussed, and the specific circumstances under which each is appropriate are identified. Building on leading-edge research and analysis in the field of life-cycle impact assessment, a modified methodology for evaluating surface area occupation is proposed. This approach is demonstrated for a series of mining practices including three individual gold mines, a bauxite mine, and a copper mine. The specific data requirements and resulting equivalency factors for each mine are discussed. Results indicate that equivalency factors for gold (average of 700 acre-yr/ton) are expected to be several orders of magnitude higher than for either bauxite (0.004 acre-yr/ ton) or copper (0.03 acre-yr/ton). These dramatic differences in results demonstrate that equivalency factors are appropriate and necessary for including land-use impact potential as part of a life-cycle assessment that includes several different minerals or material requirements.     

Life-Cycle Assessment: Constraints on Moving from Inventory to Impact Assessment

Life-cycle assessment (LCA) is a technique for systematically analyzing a product from cradle-to-grave, that is, from resource extraction through manufacture and use to disposal. LCA is a mixed or hybrid analytical system. An inventory phase analyzes system inputs of energy and materials along with outputs of emissions and wastes throughout life cycle, usually as quantitative mass loadings. An impact assessment phase then examines these loadings in light of potential environmental issues using a mixed spectrum of qualitative and quantitative methods. The constraints imposed by inventory's loss of spatial, temporal, dose-response, and threshold information raise concerns about the accuracy of impact assessment. The degree of constraint varies widely according to the environmental issue in question and models used to extrapolate the inventory data. LCA results may have limited value in two areas: (I) local and/ortransient biophysical processes and (2) issues involving biological parameters, such as biodiversity, habitat alteration, and toxicity. The end result is that impact assessment does not measure actual effects or impacts, nor does it calculate the likelihood of an effect or risk Rather, LCA impact assessment results are largely directional environmental indicaton. The accuracy and usefulness of indicators need to be assessed individually and in a circumstance-specific manner prior to decision making. This limits LCAs usefulness as the sole basis for comprehensive assessments and the comparisons of alternatives. In conclusion, LCA may identify potential issues from a systemwide perspective, but more-focused assessments using other analytical techniques are often necessary to resolve the issues.     

Site-Dependent Life-Cycle Impact Assessment of Acidification

The lack of spatial differentiation in current life-cycle impact assessment (LCIA) affects the relevance of the assessed impact. This article first describes a framework for constructing factors relating the region of emission to the acidifying impact on its deposition areas. Next, these factors are established for 44 European regions with the help of the RAINS model, an integrated assessment model that combines information on regional emission levels with information on long-range atmospheric transport to estimate patterns of deposition and concentration for comparison with critical loads and thresholds for acidification, eutrophication via air; and tropospheric ozone formation. The application of the acidification factors in LCIA is very straightforward. The only additional data required, the geographical site of the emission, is generally provided by current life-cycle inventory analysis. The acidification factors add resolving power of a factor of 1,000 difference between the highest and lowest ratings, while the combined uncertainties in the RAINS model are canceled out to a large extent in the acidification factors as a result of the large number of ecosystems they cover The framework presented is also suitable for establishing similar factors for eutrophication and tropospheric ozone formation for regions outside Europe as well.     

Evaluating Human and Ecological Impacts of a Product Life Cycle: The Complementary Roles of Life-Cycle Assessment and Risk Assessment

Life-cycle assessment (LCA) is a tool for evaluating various health and environmental impacts throughout a product's life. When used as a screening tool, LCA can potentially identify the processes and materials most likely to pose a threat to human health and the environment, and to determine where a risk assessment is warranted. The European Union has issued a ban on lead-based solder from use in electronic equipment beginning in July 2006. In response, the Lead-Free Solder Partnership, involving the U.S. Environmental Protection Agency, several electronics manufacturers, and the University of Tennessee afforded a vehicle for conducting a thorough LCA of leaded and lead-free solders used in the electronics industry. Sixteen impact categories were evaluated in the LCA, including human toxicity.

A primary conclusion of the assessment for human and aquatic toxicity, across the entire life cycle of tin-lead solder, was the potential for impacts derived from the landfilling of lead. These results, based on broad assumptions about exposure, suggest that a more detailed risk assessment of the landfilling process would assist in better understanding the potential for health and environmental risks. We believe LCA data can be used to identify the need for focused risk assessments, allowing the two tools to effectively complement one another. Use of both methods could assist in understanding the effectiveness of the European ban on lead solder and its potential to improve public health.     

Impact Characterization in the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts

The tool for the reduction and assessment of chemical and other environmental impacts (TRACI) is a set of life-cycle impact assessment (LCIA) characterization methods that has been developed by a series of U.S. Environmental Protection Agency research projects. TRACI facilitates the characterization of stressors that may have potential effects, including ozone depletion, global warming, acidification, eutrophication, tropospheric ozone (smog) formation, eco-toxicity, human particulate effects, human carcinogenic effects, human non-carcinogenic effects, fossil fuel depletion, and land-use effects. This article describes the methodologies developed to address acidification, eutrophication, and smog. Each of these methods offers the ability to take account of differences in expected strength of impact as a function of pollution release location within North America. Specifically, the methods employ regionalized fate and transport modeling. The resulting factors differ regionally by up to more than an order of magnitude.     

Risk Assessment and Life-Cycle Impact Assessment (LCIA) for Human Health Cancerous and Noncancerous Emissions: Integrated and Complementary with Consistency within the USEPA

The historical parallels, complementary roles, and potential for integration of human health risk assessment (RA) and Life-Cycle Impact Assessment (LCIA) are explored. Previous authors have considered the comparison of LCA and risk assessment recognizing the inherent differences in LCA and risk assessment (e.g., LCA's focus on the functional unit, and the differences in perspective of LCA and risk assessment), and also the commonalities (e.g., the basis for the modeling). Until this time, however, no one has proposed a coordinated approach for conducting LCA and risk assessment using models consistent with the U.S. Environmental Protection Agency's (USEPA's) handbooks, policies, and guidelines. The current status of LCIA methodology development can be compared to the early days of human health RA when practitioners were overwhelmed with the model choices, assumptions, lack of data, and poor data quality. Although methodology developers can build on the shoulders of the giant, LCIA requires more innovation to deal with more impact categories, more life-cycle stages, and less data for a greater number of stressors. For certain impact categories, LCIA can use many of the guidelines, methodologies, and default parameters that have been developed for human health RA, in conjunction with sensitivity and uncertainty analysis to determine the level of detail necessary for various applications. LCIA can then identify “hot spots” that require the additional detail and level of certainty provided by RA. A comparison of the USEPA's Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI) and the USEPA's Risk-Screening Environmental Indicators (RSEI) will be explored.     

A Theoretical Foundation for Life-Cycle Assessment

The presence of value judgments in life-cycle impact assessment (LCIA) has been a constant source of controversy. According to a common interpretation, the international standard on LCIA requires that the assessment methods used in published comparisons be "value free." Epistemologists argue that even natural science rests on "constitutive" and "contextual" value judgments. The example of the equivalency potential for climate change, the global warming potential (GWP), demonstrates that any impact assessment method inevitably contains not only constitutive and contextual values, but also preference values. Hence, neither life-cycle assessment (LCA) as a whole nor any of its steps can be "value free." As a result, we suggest a more comprehensive definition of objectivity in LCA that allows arguments about values and their relationship to facts. We distinguish three types of truth claims: factual claims, which are based on natural science; normative claims, which refer to preference values; and relational claims, which address the proper relation between factual knowledge and values. Every assessment method, even the GWP, requires each type of claim. Rational arguments can be made about each type of claim. Factual truth claims can be assessed using the scientific method. Normative claims can be based on ethical arguments. The values of individuals or groups can be elicited using various social science methods. Relational claims must follow the rules of logic. Relational claims are most important for the development of impact assessment methods. Because LCAs are conducted to satisfy the need of decision makers to consider environmental impacts, relational claims about impact assessment methods should refer to this goal. This article introduces conditions that affect environmental decision making and discusses how LCA—values and all—can be defended as a rational response to the challenge of moving uncertain scientific information into the policy arena.     

Bottom-Up Life-Cycle:Assessment of Product Consumption in Belgium

The present study shows the results and methodology applied to the study of the identification of priority product categories for Belgian product and environmental policy. The main goal of the study was to gather insight into the consumption of products in Belgium and their related life-cycle environmental impacts. The conclusions of this project on the product categories with major environmental contributions can be used to start up working groups involving stakeholders and initiate detailed product studies on the impact reduction potential that could be achieved by means of implementing product policy measures. Several ways of assessing product category environmental impacts and the effects of policy measures have been developed; 'bottom-up' or 'market-life-cycle assessment' is one of these, and we tried this approach for the situation in Belgium. Simplified life-cycle assessment (LCA) studies were conducted for representative average products within each function-based product category and the results were multiplied with market statistics. Using this approach, we found that building construction, building occupancy, and personal transport are among the major categories for Belgium. The major drawbacks of this approach are the system-level limitations and the existence of a broad spectrum of nonharmonized methods and datasets from which a sound preliminary selection had to be made. Consequently, the retrieval and selection of data was very time consuming and due to this we had to accept some major limitations in the study design. Nevertheless, the study has contributed to the development of a methodology for market-LCA and elements that can be picked up in currently ongoing and future work. The study concludes that to improve the feasibility and acceptance of this type of study there is a need for the development of a harmonized methodology on market-LCA, policy-relevant impact indicators as well as a harmonized and stakeholder-agreed-upon LCA databases.     

Three Strategies to Overcome the Limitations of Life-Cycle Assessment

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.     

Life-Cycle Global Warming Impact of CFCs and CFC-substitutes for Refrigeration

We have investigated the global warming potential (GWP) of CFC-I I, CFC-12, and their replacements, HCFC-I23 and HFC-I34a, based on a life-cycle methodology for refrigeration. We have extended the definition of the total equivalent warming impact (TEWI), which considers the GWP (direct) and GWP (indirect) warming potential of each chemical compound, by adding the GWP (chemical production), GWP (recycling), and GWP (atmospheric breakdown products) for each chemical. We call the new index "life-cycle warming impact" (LCWI).We find that the GWP (chemical production) contributes by no more than 1% to LCWI, and that the GWP (indirect) is highly dependent on refrigerator eficiency and the fuel mix of the electricity source used to operate the appliance. The GWP (atmospheric breakdown products) may also have a significant impact on LCWI.     

Water Resources in Life-Cycle Impact Assessment: Considerations in Choosing Category Indicators

Water is one of many resources, wastes, and pollutants considered in life-cycle assessment (LCA). The widely used indicator for water resources, the total input of water used, is not adequate to assess water resources from a sustainability perspective. More detailed indicators are proposed for water resources in two areas essential to water sustainability: water quantity and water quality. The governing principles for a consideration of water quantity are that (1) the water sources or LCA inputs are renewable and sustainable and (2) the volume of water released or LCA outputs are returned to humans or ecosystems for further use downstream. The governing principle for a consideration of water quality is that the utility of the returned water is not impaired for either humans or ecosystems downstream. Water quantity indicators are defined for water use, consumption, and depletion to reveal the sustainable or nonsustainable nature of the sources. A flexible set of water quality indicators for various factors that may impair water quality are then discussed, including the LCA study choices, technical challenges, and trade-offs involved with such indicators. Indicator selection from this set involves the underlying concern or endpoint represented by the indicator and the level and accuracy of decision-making information that the indicator must provide. With significant differences in emissions among systems studied using LCA and different purposes of the LCA studies themselves, a single, default set of water quality indicators applicable to all systems studied with LCA is problematic. The proposed water quantity and quality indicators for LCA studies are also intended to be compatible with environmental management and reporting systems so that data needs are not duplicated and interpretation for one does not contradict or sow confusion for the other.     

Product Environmental Life-Cycle Assessment Using Input-Output Techniques

Life-cycle assessment (LCA) facilitates a systems view in environmental evaluation of products, materials, and processes. Life-cycle assessment attempts to quantify environmental burdens over the entire life-cycle of a product from raw material extraction, manufacturing, and use to ultimate disposal. However, current methods for LCA suffer from problems of subjective boundary definition, inflexibility, high cost, data confidentiality, and aggregation.
This paper proposes alternative models to conduct quick, cost effective, and yet comprehensive life-cycle assessments. The core of the analytical model consists of the 498 sector economic input-output tables for the U.S. economy augmented with various sector-level environmental impact vectors. The environmental impacts covered include global warming, acidification, energy use, non-renewable ores consumption, eutrophication, conventional pollutant emissions and toxic releases to the environment. Alternative models are proposed for environmental assessment of individual products, processes, and life-cycle stages by selective disaggregation of aggregate input-output data or by creation of hypothetical new commodity sectors. To demonstrate the method, a case study comparing the life-cycle environmental performance of steel and plastic automobile fuel tank systems is presented.     

Decision Analysis Utilizing Data from Multiple Life-Cycle Impact Assessment Methods Part I: A Theoretical Basis

Numerous methodologies for the life-cycle impact assessment (LCIA) step of life-cycle assessment (LCA) are currently in popular use. These methods, which are based on a single method or level of analysis, are limited to the environmental fates, impact categories, damage functions, and stressors included in the method or model. Because of this, it has been suggested within the LCA community that LCIA data from multiple methods and/or levels of analysis, that is, end-point and midpoint indicators, be used in LCA-based decision analysis to facilitate better or, at least more informed, decision making. In this (two-part) series of articles, we develop and present a series of LCA-based decision analysis models, based on multiattribute value theory (MAVT), which utilize data from multiple LCIA methods and/or levels of analysis. The key to accomplishing this is the recognition of what LCIA damage indicators represent with respect to decision analysis, namely, decision attributes and, in most cases, proxy attributes. The use of proxy attributes in a decision model, however, poses certain challenges, such as the assessment of decision-maker preferences for actual consequences that are only known imprecisely because of inherent limits of both LCA and scientific knowledge. In this article (part I), we provide a brief overview of MAVT and examine some of the decision-theoretic issues and implications of current LCIA methods. We illustrate the application of MAVT to develop a decision model utilizing damage indicators from a single LCIA methodology; and, we identify the decision-theoretic issues that arise when attempting to combine LCIA indicators from multiple methods and/or levels of analysis in a single decision model. Finally, we introduce the use in our methodology of constructed attributes to combine related end-point damage indicators into single decision attributes and the concept and evaluation of proxy attributes.     

An Environmentally Conscious Decision Support System for Life-Cycle Management

An Internet-based environmentally conscious decision support tool (EcoDS) has been developed for life-cycle management EcoDS involves an initial vertical streamlining step, where the significant life-cycle stages, stressors, and impact categories are selected and cross-correlated. Because the streamlining is performed prior to the inventory, the approach expedites data collection. Comparisons among alternative product designs or manufacturing processes are based on two metrics: financial risk (or cost) and "residual" risk. For purposes of evaluation these two indicators are individually aggregated using a user or organization-specified value system. A salient feature of EcoDS is that this output can be condensed into a single summary matrix akin to a hybrid pro forma income statement and environmental balance sheet. The clear delineation between the tradeoffs involved in each alternative facilitates decision making by upper management. A case study on painting attematives is presented to illustrate the methodology     

Avoiding Co-Product Allocation in Life-Cycle Assessment

Abstract: In a life‐cycle assessment (LCA) involving only one of several products from the same process, how are the resource consumption and the emissions associated with this process to be partitioned and distributed over these co‐products? This is the central question in co‐product allocation, which has been one of the most controversial issues in the development of the methodology for life‐cycle assessment, as it may significantly influence or even determine the result of the assessments. In this article, it is shown that in prospective life‐cycle assessments, co‐product allocation can always be avoided by system expansion. Through a number of examples, it is demonstrated how system expansion is performed, with special emphasis on issues that earlier have been a focus of the allocation debate, such as joint production (e.g., of chlorine and sodium hydroxide, zinc and heavy metals, and electricity and heat), the handling of “near‐to‐waste” by‐products, processes simultaneously supplying services to multiple product systems, and credits for material recycling and downcycling. It is shown that all the different co‐product situations can be covered by the same theoretical model and the same practical procedure, and that it is also possible to include the traditional co‐product allocation as a special case of the presented procedure. The uncertainty aspects of the presented procedure are discussed. A comparison is made with the procedure of ISO 14041, “Life‐cycle assessment—Goal and scope definition and inventory analysis,” the international standard.     

Institutionalization of Life-Cycle Thinking in the Everyday Discourse of Market Actors

The widespread popularity of life-cycle assessment (LCA) is difficult to understand from the point of view of instrumental decision making by economic agents. Ehrenfeld has argued, in a 1997 issue of this journal, that it is the world-shaping potential of LCA that is more important than its use as a decision-making tool. The present study attempts to explore the institutionalization of this "LCA world view" among ordinary market actors. This is important because environmental policy relies increasingly on market-based initiatives. Cognitive and normative assumptions in authoritative LCA documents are examined as empirical data and compared with data from focus group interviews concerning products and the environment with "ordinary" manufacturers, retailers, and consumers in Finland. These assumptions are (1) the "cradle-to-grave" approach, (2) the view that all products have an environmental impact and can be improved, (3) the relativity of environmental merit, and (4) the way responsibility for environmental burdens is attributed. Relevant affinities, but also differences, are identified. It is argued that life-cycle thinking is not primarily instrumental, but rather is gaining a degree of intrinsic value. The study attempts to establish a broader institutional context in which the popularity of LCA can be understood. From the point of view of this broader context, some future challenges for the development of LCA and life-cycle thinking are suggested.     

Using Life-Cycle Assessment in Process Design

This article presents the application of life-cycle assessment in early phases of process design in the context of technology that employs a bio-based material. The goal is to identify hot spots in the process chains with regard to environmental impacts by performing a dominance analysis. By focusing his activities on the hot spots identified, the designer is given the opportunity to efficiently improve environmental performance. This approach is illustrated for the case of supercritical water gasification, a novel technology for the treatment of organic feedstock with high moisture content. In the reactor under supercritical conditions, organic components are converted into a high-caloric synthesis gas, with hydrogen, methane, and carbon dioxide as the main products. The data used for the assessment are obtained from laboratory tests and the literature, completed by assumptions for missing data. The scope of assessment ranges from the extraction of raw materials to the product, that is, hydrogen (cradle to gate) with sewage sludge of a municipal wastewater treatment plant used as feedstock. The assessment identifies the main sources of environmental impacts. The predominant process step in terms of global warming potential is the supply of the gasification process with additional heat. The production of a blending agent in the dewatering step is the main source of the impact category of acidification, whereas the wastewater treatment plant is the origin of emissions that lead to eutrophication. The revealed sources are analyzed further and options for reducing the environmental impacts are discussed.