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Technologies That Help Clean Up Emissions from a Power Plant

During the middle of the 20th century, people became aware of the dangers that air pollution posed to public health. The federal and state governments began passing legislation to reduce air pollution, which culminated in a series of Clean Air Acts between 1970 and 2006. This legislation authorized the U.S. Environmental Protection Agency (EPA) to set limits on certain air pollutants. In the last half of the 20th century, scientists began exploring new technologies for reducing toxic emissions in power plants.

  1. Scrubbers

    • Sulfur dioxide is an impurity found in coal. It produces acid rain when released into the atmosphere. Scientists began developing scrubbers, which are built into the stacks, or flues, to remove this gas from power plant emissions. As coal is burned in power plants, it emits gases through a stack. Scrubbers are designed to remove sulfur dioxide and nitrogen oxides from these emissions, before they are released into the atmosphere. They divert the flue gas through a tower, where a water and limestone mixture sprays it. The sulfur dioxide reacts with the limestone to produce gypsum, a substance used in the production of wallboard and as an additive in concrete. The remaining water vapor exits the stack.

    Carbon Sequestration

    • Carbon sequestration is a technique designed to help reduce the amount of greenhouse gases, such as carbon dioxide, emitted by coal combustion in power plants. It captures, separates, and stores carbon dioxide without adversely affecting energy use or hampering economic growth. The National Energy Technology Laboratory (NETL), a laboratory owned and operated by the U.S. Department of Energy, leads carbon sequestration research and development efforts in the U.S. The process begins with the separation and capture of carbon dioxide from power plant flue gas. The primary method for storing carbon dioxide is to inject it into underground geological formations, such as unmineable coal seams or gas and oil reserves. Currently, carbon sequestration is an expensive process. The NETL's goal is to make this technology available for commercial use in 2020.

    Clean-Burning Fuels

    • Coal produces 54 percent of the electricity generated in the United States, according to the Union of Concerned Scientists. Burning coal in power plants releases pollutants, which are leading causes of global warming, smog, and acid rain. Power plants also create wastes, such as sludge and ash, which include toxic substances, such as mercury and arsenic. Switching to clean-burning fuels, for example natural gas, helps to reduce these emissions. Natural gas emits small amounts of sulfur dioxide, lower levels of carbon dioxide, and almost no ash.

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