Electricity explained Electricity and the environment

 

Electricity explainedElectricity and the environment

Although electricity is a clean and relatively safe form of energy when it is used, 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 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.

The two coal-fired power plants of the Crystal River North Steam Complex in Crystal River, Florida

Source: Ebyabe, Wikimedia Commons author (GNU Free Documentation License) (public domain)

Fossil fuel, biomass, and waste burning power plants

In the United States, about 61% of total electricity generation in 2021 was produced from fossil fuels (coal, natural gas, and petroleum), materials that come from plants (biomass), and municipal and industrial wastes. The substances that occur in combustion gases when these fuels are burned 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, which 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 reduce air pollution emissions in various ways

Air pollution emission standards limit the amounts of some of the substances that power plants can release into the air. Some of the ways that power plants meet these standards include:

• Burning low-sulfur-content coal to reduce SO₂ emissions. Some coal-fired power plants cofire wood chips with coal to reduce SO₂ emissions. Pretreating and processing coal can also reduce the level of undesirable compounds in combustion gases.
• Different kinds of particulate emission control devices treat combustion gases before they exit the power plant:
  • 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.

Hunter Power Plant, a coal-fired power plant south of Castle Dale, Utah

Source: Tricia Simpson, Wikimedia Commons author (GNU Free Documentation License) (public domain)

Many U.S. power plants produce CO₂ emissions

The electric power sector is a large source of U.S. CO₂ emissions. Electric power sector power plants that burned fossil fuels or materials made from fossil fuels, and some geothermal power plants, were the source of about 32% of total U.S. energy-related CO₂ emissions in 2021.

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 retention ponds. Most of these ponds are unlined and pose risks to ground water. 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.

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.