To develop sound policies, policy makers must understand the relative environmental impacts of alternative energy sources, including how the impacts of renewable energy technologies compare to those of fossil-fuel technologies and to opportunities for improvements in energy efficiency. Understanding the potential environmental impacts of renewable energy technologies is also essential for identifying and pursuing designs, manufacturing methods, project siting, utitlity operations, and so on to mitigate or offset these effects.

Environmental impacts of energy sources are commonly assessed on two scales or levels of aggregation. The first scale is the regional or national scale, which is an attempt to characterize the average impact of a typical facility or installation for the purposes of broad comparisons and planning. Life cycle assessment (LCA), for example, is an attempt to account for the full suite of impacts associated with all stages of an energy project, from the extraction of raw materials to the decommissioning of a facility and the disposal of equipment. The second scale is on the local level, where site-specific impacts, such as effects on wildlife and local water supplies, can be assessed.

The first part of this chapter provides a review of published LCAs as a basis for comparing renewable and fossil-fuel technologies in terms of emissions and energy, land, and water requirements. Detailed LCAs for selected renewable energy technologies are provided in Appendixes B-D of this report. The second half of the chapter provides a discussion of local-scale impacts and permitting and regulatory requirements in the United States and China, with examples illustrating some of the environmental concerns raised by renewable energy projects. Localized effects will warrant more attention as renewable energy deployment accelerates, especially in places where large-scale installations are being considered. The last part of the chapter identifies opportunities for collaboration by the United States and China to advance renewable energy technology by minimizing harmful effects on human health and the environment.

FOSSIL FUEL VS. RENEWABLE ELECTRICITY GENERATION

An LCA estimates resource requirements, energy use, and environmental impacts of products or services at all life stages. The estimates may be derived from detailed, “bottom-up” analyses of mining, manufacturing, transport, construction, operations, and disposal processes or from “top-down” analyses based on national-scale economic input/output models. Overall, an LCA is useful for comparing impacts of different technologies and for identifying points in the life cycle where improvements can be made.

In this section, we present results from published LCA studies compiled by the National Academies Committee on Electricity from Renewable Resources: Status, Prospects, and Impediments (NAS/NAE/NRC, 2010a). These studies provide high-level comparisons of fossil- and renewable-fueled technologies in



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