Wind-powered generation systems do not directly emit pollutants into the environment during operation. Some air pollutant emissions, mostly from internal combustion engines, may occur during maintenance operations, but such emissions would be minimal. Much of the environmental impact associated with a wind turbine is likely to occur during construction, major maintenance, and decommissioning phases, all of which would be due to increased vehicular traffic and operation of on-site machinery. Because wind turbines are often located in remote areas, construction and use of roads to the turbines would result in environmental damage through soil disturbance, potential changes in water runoff and road dust emissions, and impacts to wildlife habitats.
It must be noted that these environmental impacts will necessarily be multiplied due to the large number of units that are projected to be installed. If large numbers (more than 100) of turbines are installed at a single site, these impacts may change significantly (either positively or negatively). For instance, a concentrated wind energy site may have continual maintenance operations that would result in ongoing vehicular and machinery emissions, but could also result in less land area used for roads. As is the case with solar energy, wind energy will require additional electricity transmission lines, which will also result in environmental impacts associated with construction, habitat and soil disturbance, and periodic vehicle traffic.
On a unit energy output basis, wind generation has been estimated to have the lowest life cycle CO2 emissions of any of the alternatives (see White and Kulcinski , cited in Meier e2 t al. ).
The primary on-going environmental impacts of wind energy sites are noise, changes to visual resources, and collisions of birds and bats . The Programmatic Environmental Impact Statement (PEIS) prepared by the Bureau of Land Management (BLM) was developed to evaluate the potential impacts associated with a proposed Wind Energy Development Program on BLM lands in nine western U.S. states . The PEIS provides a comprehensive overview of the potential environmental impacts associated with construction, operation, and decommissioning of wind turbines from a general perspective, as opposed to evaluating the site-specific impacts.
The noise and visual resource issues have significant impacts when wind turbines are located near populated areas, although impacts to visual resources may be greater in currently undeveloped areas where people are accustomed to views without wind turbines. It is unclear how wind turbine noise may impact wildlife. The BLM PEIS notes that several studies have shown reduced densities of some species in habitats adjacent to roads, and at least one study attributed the reduction to elevated noise levels. In other studies, the BLM PEIS notes that the adverse noise effects on raptors were "in many cases" temporary, with the raptors becoming "habituated to the noise" .
The BLM PEIS reviewed several studies of bird and bat mortality due to collisions with turbines, towers, and transmission lines, and cited studies in locations from California to Massachusetts that estimated the number of bird fatalities to be from 0 to 4.45 fatalities per turbine per year. There was little apparent correlation between sites, with two large (2,900+ turbines each) California sites varying in mortality rates by roughly an order of magnitude (0.33-2.31 fatalities per turbine per year), and a site in West Virginia with on 44 turbines having a mortality rate of just over 4 fatalities per turbine per year . It appears that there are significant site-specific factors that determine the bird impact rate, but those factors are currently not known.
Large-scale implementation of wind energy can also impact the broader climate by extraction of energy from the atmosphere . The impacts on wind patterns and possibly precipitation patterns are estimated to be measurable, but are expected to have negligible effects on global surface temperature. Considerable research is needed to more accurately evaluate these impacts.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.