Assessment of Environmental Life-Cycle Approach for Industrial Materials and Products
by Steven B. Young
Degree of Doctorate of Philosophy
Graduate Department of Metallurgy and Materials Science
University of Toronto
Environmental life cycle assessment (LCA) was evaluated as an approach for analysis of potential environmental impacts associated with the production of industrial materials and of product systems. It was the goal also to consider possibilities for environmental improvement via materials selection and design.
Based on the LCA approach, a methodology was devised for process-by-process quantification of resource inputs and environmental outputs. Three indicators of potential environmental impacts (gross energy requirement, global warming potential, and solid waste burden) were employed. Using data from the literature, inventory and ecoprofile results were calculated for the production of three materials (integrated steel, primary aluminum and high-density polyethylene). Energy production systems were also analysed. The life-cycles of two generic product systems (a beverage package in 355 mL and 1 L size formats and a structural automotive component) were also analyzed since each might be formed from one of the three materials studied.
Base case results were generated for conditions and assumptions representing average practices. Sensitivity analyses were supported by two measures of data uncertainty: range-due-to-practice and range-due-to-estimate, where the latter considered possible measurement errors, variable estimates of emissions, and judgments concerning indicator indices. Product analyses illustrated how materials influence potential life-cycles burdens. Indicators showed that, for the short-lived packaging product, environmental burdens were largely associated with materials production; in contrast, for the durable, longer-lived automotive component, loadings were largely at the product use-stage.
Four types of general product systems were categorised based on where the majority of impacts are incurred (i.e., at materials production, manufacture, product use, or end-of-life). The concept of extrinsic environmental properties was proposed to help incorporate environmental criteria into materials selection. A materials selection chart and product life-cycle mapping were discussed for design.
A new framework for LCA was proposed. It discerns two basic methodological steps (the life-cycle inventory and interpretation) across three dimensions (physical, analytical, valuative) which correlate to two categories of application (operations-specific and strategic). It was concluded that the LCA approach can provide and structure product-focused environmental information, and aid judgment in a design-for-environment program.