Environmental Tradeoffs Associated with Various Energy Paths: A Total Energy Cycle Analysis Approach

As our understanding of the physical impacts of technology use on the environment has increased, we have begun to alter the way choices among energy alternatives are made. Energy supply and demand decisions have traditionally been driven primarily by cost factors, but as public awareness of environmental issues has increased, environmental assessments are becoming an important part of the selection process. A principal question is: what are the environmental tradeoffs associated with various energy pathways? Simple answers are sometimes misleading. Some adverse environmental impacts are associated with technologies that are usually thought to be relatively benign. In order to carry out an equitable comparison of alternative energy pathways, we must be able to characterize not only the primary "energy-production" and "end-use" stages of an energy pathway, but the full process of providing an energy service. This can be accomplished using a "total energy cycle analysis" approach. This approach considers all stages of an energy cycle including raw material extraction, material transportation, raw material transformation to a refined energy form, energy storage and distribution, and end use. The full life cycles (from construction through operation to dismantling/ disposal) of the facilities and equipment needed in each of these stages are also considered. In addition, environmental impacts of the materials embodied in the energy infrastructure (e.g., the emissions from concrete, metals, and other materials) should be considered, since technologies differ in their material intensities and therefore vary in their secondary effects on the environment. In recognition of the increasing need for comprehensive analysis in the decision-making process, a methodology that establishes the principles and assumptions to be used in total energy cycle analyses is being developed. There are, of course, many uncertainties and complexities associated with quantifying these environmental impacts, and these uncertainties will have to be appropriately reflected in the methodology.