Estimation of environmental implications of construction materials and designs using life cycle assessment techniques.

摘要

The concepts of sustainable development and "environmental friendliness" have lately become very important to government and industry. Increasing public and regulatory pressures have inspired varying degrees of activity. The construction industry has paid particular attention to the ecological impacts of new facilities, energy use of buildings, asbestos contamination and removal, indoor air quality, and several other important environmental issues. Yet many impacts relative to constructed facilities' life cycle (planning, design, construction, occupancy/operation, and demolition) have not been systematically and comprehensively studied. Engineers and architects, as well as owners, planners, operators and other construction professionals should understand the environmental and energy implications of construction materials, processes and alternative facility designs because their everyday decisions carry substantial social implications. The objective of this thesis is to provide information, metrics and analysis tools related to the environmental implications of construction materials and alternative design choices in construction. In particular, this thesis compares in three case studies the environmental effects of asphalt and reinforced cement concrete pavements, steel and reinforced concrete bridge girders, and wood and light-gauge steel framing for residential applications. Systems-level analysis is performed using Life Cycle Assessment/Analysis (LCA) techniques. A primary tool used in the analysis is the Economic Input-Output LCA (EIO-LCA) method developed by Carnegie Mellon University's Green Design Initiative research group. Additional data and information, primarily for the use and disposal life cycle stages, have been collected from literature. The inputs of material production quantified include the use of fuel, electricity, ores and fertilizers, and the environmental emissions (outputs) quantified include toxic chemical releases, ozone depletion potential, conventional air pollutant emissions, and hazardous waste generation and management.; The results indicate that determining which alternative in a comparison is better solely on environmental terms can be difficult. Uncertainties in the data used in the analysis call for careful interpretation of the results. Differences in the longevity of design alternatives may make one alternative "environmentally friendlier" when the impacts are annualized. The manufacturing life cycle stage has larger environmental effects for the three case studies than the use and disposal stages. For asphalt and cement concrete pavements, asphalt appears to be a more environmentally sustainable selection due to its environmentally beneficial high recycling rates. Reinforced concrete girders for bridges appear to have lower overall environmental burdens than steel girders. The study of wood framing vs. light-gauge steel framing for homes indicates that wood framing has lower environmental impacts.