Although electricity is a clean and relatively safe form of energy, the generation and transmission of electricity affects the environment. Nearly all types of electric power plants have an effect on the environment, but some power plants have larger effects than others.
The two coal-fired power plants of the Crystal River North Steam Complex in Crystal River, Florida
Hunter Power Plant, a coal-fired power plant south of Castle Dale, Utah
The United States has laws that govern the effects that electricity generation and transmission have on the environment. The Clean Air Act regulates air pollutant emissions from most power plants. The U.S. Environmental Protection Agency (EPA) administers the Clean Air Act and sets emissions standards for power plants through various programs such as the Acid Rain Program. The Clean Air Act has helped to substantially reduce emissions of some major air pollutants in the United States.
The effect of power plants on the landscape
All power plants have a physical footprint (the location of the power plant). Some power plants are located inside, on, or next to an existing building, so the footprint is fairly small. Most large power plants require land clearing to build the power plant. Some power plants may also require access roads, railroads, and pipelines for fuel delivery, electricity transmission lines, and cooling water supplies. Power plants that burn solid fuels may have areas to store the combustion ash.
Many power plants are large structures that alter the visual landscape. In general, the larger the structure, the more likely it is that the power plant will affect the visual landscape.
Fossil fuel, biomass, and waste burning power plants
In the United States, about 67% of total electricity generation in 2016 was produced from: fossil fuels (coal, natural gas, and petroleum), materials that come from plants (biomass), and municipal and industrial wastes. Emissions that result from combustion of these fuels include:
- 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 effects on the environment and human health:
- CO2 is a greenhouse gas, and it contributes to the greenhouse effect.
- 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.
- NOx contribute to ground level ozone, which irritates and damages the lungs.
- PM results in hazy conditions in cites and scenic areas, 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.
- Heavy metals such as mercury are hazardous to human and animal health.
Power plants use air emission controls to reduce emissions
Air pollution emission standards limit the amounts of some of the substances that power plants can release into the air. Power plants meet these standards in several ways:
- Burning low-sulfur-content coal reduces SO2 emissions. Pretreating and processing coal can also reduce the level of undesirable compounds in combustion gases.
- PM emission control devices that treat combustion gases before they exit the power plant include:
- Bag-houses are large filters that trap particulates.
- Electrostatic precipitators use electrically charged plates that attract and pull particulates out of the combustion gas.
- Wet scrubbers use a liquid solution to remove PM from combustion gas.
- Wet and dry scrubbers mix lime in the fuel (coal) or spray a lime solution into combustion gases to reduce SO2 emissions. Fluidized bed combustion also results in lower SO2 emissions.
- NOx emissions controls include low NOx burners during the combustion phase or selective catalytic and non-catalytic converters during the post combustion phase.
Some power plants also produce liquid and solid wastes
Ash is the solid residue that results from burning solid fuels such as coal, biomass, and municipal solid waste. Bottom ash includes the largest particles that collect at the bottom of the combustion chamber of power plant boilers. Fly ash is the smaller and lighter particulates that collect in air emission control devices. Fly ash is usually mixed with bottom ash. The ash contains all the hazardous materials that pollution control devices capture. Many coal-fired power plants store ash sludge (ash mixed with water) in rentention ponds. Several of these ponds have burst and caused extensive damage and pollution downstream. Some coal-fired power plants send ash to landfills or sell ash for use in making concrete blocks or asphalt.
Most power plants produce greenhouse gases
Electricity generation is one of the leading sources of greenhouse gas emissions in the United States. Power plants that burn fossil fuels or materials made from fossil fuels, and some geothermal power plants, are the sources of nearly 40% of total U.S. energy-related CO2.
Nuclear power plants produce different kinds of waste
Nuclear power plants do not produce greenhouse gases or PM, SO2, or NOx, but they do produce two general types of radioactive waste:
- Low-level waste, such as contaminated protective shoe covers, clothing, wiping rags, mops, filters, reactor water treatment residues, equipment, and tools, is stored at nuclear power plants until the radioactivity in the waste decays to a level safe for disposal as ordinary trash, or it is sent to a low-level radioactive waste disposal site.
- High-level waste, which includes the highly radioactive spent (used) nuclear fuel assemblies, must be stored in specially designed storage containers and facilities (see Interim storage and final disposal in the United States).
Electric power lines and other distribution infrastructure also have a footprint
Electricity transmission lines and the distribution infrastructure that carries electricity from power plants to customers also have environmental effects. Most transmission lines are above ground on large towers. The towers and power lines alter the visual landscape, especially when they pass through undeveloped areas. Vegetation near power lines may be disturbed and may have to be continually managed to keep it away from the power lines. These activities can affect native plant populations and wildlife. Power lines can be placed underground, but it is a more expensive option and usually not done outside of urban areas.