• Environmental Impact of Power Plants

    All energy conversion methods used to produce electricity have some environmental impact. The impact may have an active effect like the emission of airborne pollutants, or may have a passive effect like aesthetics (beauty of nature) or habitat (natural environment of an animal, plant, or other organism) modification. Even methods considered environmentally friendly, like wind, solar, and hydro, have some impact on the environment. Thus every electricity generation plant has an environmental impact. The transmission of electricity with concerns over electromagnetic fields, aesthetics, and land use, also impacts the environment.

    The whole cycle of electricity generation must be considered when looking at the environmental impact. This includes the production and transportation of fuel for the conversion process. This is especially true of fossil fuel and nuclear power plants, which use large quantities of fuel taken from the earth. Energy system environmental impact consists of fuel recovery and production, fuel transportation, electricity transmission, and spent fuel emissions.


    Environmental Effects of Raw Fuel Production

    A. Coal Production: Coal is almost exclusively produced for electrical generation. Coal production is often viewed as only a local environmental problem. Coal mining, particularly surface mining, has both long-term and short-term effects on land, including dust, noise, and water drainage/runoff. Preparation of coal produces both solid and liquid waste of which must be treated and disposed. Transportation of coal and its storage produces dust which results in water runoff problems that can kill aquatic life, and make our waterways an unhealthy place to live, work, and play.


    B. Oil Production: The fuel oil burned in power plants is a byproduct of the petroleum industry, so electricity production is partially responsible for environmental issues associated with oil and hydrocarbon burning. This fuel burning produces many "greenhouse" gases. Other environmental impacts associated with oil production include blowouts, spills, brine disposal, and the production of hydrogen sulfide. Transportation of oil involves spill and leak hazards. Oil refining includes environmental effects such as explosions, fires, hydrocarbon emissions, noise, odor, and water runoff.


    C. Natural Gas Production: During the natural gas production, possible environmental effects include blowouts, leaks, hydrocarbon emissions, and trace metal emissions. The treatment of natural gas involves air emissions and the disposal of liquid residuals, while transportation and storage effects include spills and explosions.


    D. Uranium Production: Uranium mining involves concerns such as radioactive dust releases, mine water seepage, protection of workers from radioactivity, and the disposal of a large quantity of mine waste containing a low level of radioactivity. Uranium treatment must dispose of mill tailings containing toxic metals and chemical wastes used in the treatment process, as well as radiological waste. The treatment of raw uranium also must deal with radioactive dust releases. The enrichment of uranium ore must account for liquid and gaseous effluent releases, and must recycle fission products. Transportation involves the hazard of the accidental release of radioactive particles.


    Environmental Effects of Electricity Generation

    Fossil fuel power plants generally have the most widespread effect on the environment, as the combustion process produces airborne pollutants that spread over a wide area. Nuclear power plants have the most potentially dangerous effect. An operating accident at a nuclear station could release huge radioactive particles. Solar, hydro, and wind power plants generally have smaller effects on the environment.


    A. Fossil Fuel Power Plants

    Fossil fuel power plants produce environmental problems including land and water use, air emissions, thermal releases, climatic and visual impacts from cooling towers, solid waste disposal, ash disposal (for coal), and noise. Due to the need for large amounts of steam, plants can have a great effect on water use. For example, a typical 500 MW coal fired power plant uses 25 x 109 l/GW-year of water, which must be taken from water source, and then cooled to return to the water source with as little environmental effect as possible. The biggest effect fossil fuel plants have overall is the emission of air pollutants, particularly SOX, NOX , CO, CO2 , and hydrocarbons. Carbon monoxide, CO, carbon dioxide, CO2, and the hydrocarbons are the "greenhouse gases," believed to be responsible for global warming. SOX and NOX produce acid when released into the atmosphere, leading to the production of acid rain. Table list approximate amounts of airborne pollutants produced. Generally, air emissions are controlled by the use of scrubbers and precipitators located at the plant.


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    Table: Power Plant Emissions (g/kWh)

    The energy sources for electricity generation are: fossil fuels (mainly coal, oil, and natural gas), materials that come from plants (biomass), and municipal and industrial wastes. Combustion of these fuels result for emissions of:

    Carbon dioxide (CO2)                   Carbon monoxide (CO)

    Sulfur dioxide (SO2)                     Nitrogen oxides (NOx)

    Particulate matter (PM)                 Heavy metals such as mercury

    Nearly all combustion byproducts have negative impacts on the environment and human health:

    1. CO2 is a greenhouse gas, and it contributes to the greenhouse effect.

    2. SO2 causes acid rain, which is harmful to plants and to animals that live in water. SO2 also worsens respiratory illnesses and heart diseases, particularly in children and the elderly.

    3. NOX contribute to ground level ozone, which irritates and damages the lungs.

    4. PM (solid or liquid hazardous particles suspended in air) results in hazy conditions in cites and scenic areas (views of impressive or beautiful natural scenery), and coupled with ozone, contributes to asthma and chronic bronchitis, especially in children and the elderly. Very small, or fine PM, is also believed to cause emphysema and lung cancer.

    5. Heavy metals such as mercury are hazardous to human and animal health.

    Natural gas is a fossil fuel, though the global warming emissions from its combustion are much lower than those from coal or oil. Natural gas emits 50 to 60 percent less carbon dioxide (CO2) when combusted in a new, efficient natural gas power plant compared with emissions from a typical new coal plant. The drilling and extraction of natural gas from wells and its transportation in pipelines results in the leakage of methane, primary component of natural gas that is 34 times stronger than CO2 at trapping heat over a 100-year period and 86 times stronger over 20 years. Thus the leakage of natural gas has adverse effect on environment.


    B. Nuclear Power Plants

    Nuclear power plants do not produce greenhouse gases or PM, SO2, or NOX, but they produce radioactive waste. An accident at a nuclear power plant may release large amounts of radioactive particles, possibly resulting in a direct loss of life, and rendering a large land area immediately unlivable. Low-level radioactive waste is stored at nuclear power plants until the radioactivity in the waste decays to a level where reactor operators can dispose of it as ordinary trash, but the disposal of the high level nuclear waste contained in spent fuel rods is a challenging task. Spent (used) nuclear fuel assemblies are very hot and highly radioactive. Such highly radioactive element initially store in specially designed pools of water resembling large swimming pools because water conveniently provide both cooling and shielding. After about five years it can be transferred into dry ventilated concrete containers, but otherwise it can safely remain in the pool indefinitely - usually for up to 50 years.

    A long term issue is the decommissioning of nuclear power plants. Decommissioning is shutting down a nuclear plant after its operational life is over. At this point the entire reactor vessel becomes a high level radioactive waste that must be disposed. The current methods of decommissioning a plant are to completely remove and dispose of all radioactive components, to entomb the reactor in concrete, or simply to shut the plant down and restrict access until the radioactivity dies out.


    C. Hydro Power Plants

    The use of hydropower to produce electricity can have both positive and negative effects on the environment. At some sites, a dam may help with flood control, flow regulation, or the reservoir may provide recreational opportunities. At other sites, the dam may have adverse effects on the hydrologic cycle, water quality of the stream, stream ecology, fish migration, and cause the destruction of landscapes (visible features of land) and ecosystems. Building new high-head dams require the displacement and compensation of populations. Low-head dams generally have a benign effect on the environment. Dam failures can lead to catastrophic floods.


    D. Wind Power Plants

    Wind generators biggest environmental effects come from visual pollution, noise, and TV interference (TV signals are reflected by the blades and tower i.e., scattering of signals). This is particularly true for wind farms, where 50 or more wind turbines are mounted at the same site. Wind farms situated on a migratory path may pose major hazards to birds. There is also a safety hazard in case of blade breakage.


    E. Solar Power Plants

    The production of electricity from solar energy sources generally has a small effect on the environment. There are no residuals produced in the energy conversion process. The only exception is solar thermal processes, which have an operating fluid that must occasionally be discharged. However, there are some environmental concerns. Bulk solar plants generally require a large land area, and they produce a great deal of heat. An unknown quantity in solar energy is the disposal of photovoltaic cells. The most promising solar cells use gallium arsenide, a toxic substance.