Modeling the energy and environmental impacts of large-scale material systems.

摘要

The extraction, processing, use, management, and disposal of material form the basis of our physical economy. These activities are the source of nearly all human impacts on the environment and define how we relate to nature. In order to understand and quantify these impacts, materials must be analyzed in terms of systems: stocks of material in use or otherwise, networks of material flows among regions or sectors of the economy, all with associated, or embedded, environmental impacts as they move around the system. This study uses various analytical tools, including life cycle assessment and substance flow analysis, to model material systems and their associated, location-specific environmental impacts for several technologically important products.;A review of relevant materials modeling literature is followed by an assessment of global emissions of silver and their associated toxicity impacts, disaggregated for 55 countries. Emissions occur from various stages in the technological cycle of silver, and from indirect sources such as power generation and cement production. Another study treats the environmental impacts of metal production, quantifying energy use and greenhouse gas emissions associated with nickel for all major production sites in the world. The facility-level assessment shows energy inputs varying by a factor of 200 on a contained nickel basis, suggesting large uncertainties in the use of global average life cycle inventory data. Two analyses examine the environmental impacts of product substitution, the first by spatially mapping net atmospheric mercury emissions from the replacement of an incandescent bulb for lighting with a compact fluorescent lamp, which vary widely among the 50 United States as well as globally. Variability depends on a number of factors associated with local electricity production and lamp recycling. The second study considers the whole system of material reuse and virgin product substitution for industrial byproducts in Pennsylvania and quantifies energy and emissions benefits. The embedded energy saved through this reuse is greater than that generated by the entire state's non- hydro renewables sector.;The results consistently show large variability depending on location and reinforce the need for geographic specificity in evaluations of environmental impacts associated with materials and products.