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This paper explores the robustness of materials selection decisions when using various life-cycle assessment methods. Improving the environmental performance of vehicles is a topic of growing concern met by today’s designer. One approach to this goal is through vehicle mass reduction, enabled through the implementation of a growing array of material candidates. While LCA methods are available to provide quantitative input into this selection decision, LCA applications are evolving and distinct. Specifically, this paper surveys the major analytical variations of LCA implementations and explores the implications of one major variant when applied to an automotive materials selection case study involving aluminum. This case study examines analytical variations in treatment of recycling by exploring allocation methods that affect product EOL. Preliminary results indicate that the choice of analytical method can have real impacts on individual metrics and there are sets of analytical variation over which strategic results are strongly affected. Introduction: The Challenge of Environmentally Informed Materials Selection Corporate regulations, resource availability, ethical responsibility, and consumer demand for environmentally-beneficial products and services currently challenge industries to conduct operations in ways that protect the natural environment, human health, and societal interests – ways that are sustainable [1]. Within the family of decisions about product and production, no single decision has greater fundamental impact on environmental performance than the selection of materials, influencing the choice of production technology, product form, and configuration and distribution of the supply chain. As such, materials establish the environmental profile of their associated extraction and refining, the characteristics of transformation into product, the product performance during use, and the potential for recovery at end-of-life (EOL). Consequently, effective tools to inform the environmental implications of materials selection decisions are critical to realizing sustainable industry. Of the methods available to incorporate environmental information into the materials selection process, the most general and broadly discussed is life cycle assessment. LCA requires the analyst to extensively characterize each stage of a product’s or process’ life, presenting a challenge for typical materials selection decisions occurring early in product development cycles, when options are ample, but data is scarce. As a result, a critical question emerges concerning the effectiveness of LCA to support materials selection decisions: Can LCA results resolve the environmental performance of materials alternatives given the level of uncertainty endemic to materials selection? 1 The key elements of LCA will be detailed in the following section. The analyses in this paper explore this question in the context of a case of materials choice for automotive structural materials. Specifically, these analyses characterize the robustness of the LCA result to variation in analytical treatment of EOL processing. The following sections briefly review the LCA method and describe the case study that will be explored. Background: Life Cycle Assessment The LCA framework is widely used to evaluate the environmental performance of product systems, offering a way to explore options that potentially will reduce life-cycle environmental impact. The International Organization for Standardization (ISO) LCA framework is depicted in Figure 1, showing the major conceptual stages of the LCA process. The Goal and Scope Definition stage is used to outline study objectives and necessary system boundaries. The next stage, Inventory Analysis, quantifies all material and energy inputs and outputs. The Impact Analysis stage then translates this inventory into impacts on ecological and human health. However, many LCA studies stop short of the Impact Analysis step due to its subjective, controversial nature and instead focus on assembling and analyzing life-cycle Inventory Analysis data. Determining the appropriate weighting method to apply depends on the strategic intent of the LCA study, and is left to the LCA decision-maker. It is this notion of explicit and implicit trade-offs that occurs when apportioning and weighting an inventory in terms of environmental effects that serves as motivation for testing the robustness of the LCA methodology. Figure 1. ISO 14040 framework for LCA [2] Exploring Materials Selection using LCA: Generic Vehicle Life Cycle To address the robustness of the LCA methodology, the authors have previously used LCA to compare implications of material selection on the life cycle of a generic vehicle. Specifically, a Base Case and Comparator vehicle, differing only in choice of material application to vehicle structural panels, were evaluated in terms of environmental impact using different LCA valuation methods. Figure 2 and Figure 3 show the impact of changing the underlying assumptions about vehicle use on the percent difference between the Base Case and Comparator analysis as defined by Equation (1) using three LCA impact methods; Cumulative Energy Demand (CED), Environmental Priorities System (EPS), and Eco-Indicator 99. These figures compare the “crossover” time between the Base Case and Comparator vehicles; the elapsed lifetime at which the environmental burden associated with material production and use of one material alternative equals that of the other. Specifically, these plots show how percent difference changes with variation in vehicle lifetime, vehicle fuel economy of the Base Case vehicle, and average driving distance per year.