Coal ash storage
Coal ash storage refers to the management of the by-products generated from burning coal, known as coal combustion by-products (CCBs). There are four main types of coal ash: fly ash, bottom ash, boiler slag, and flue gas desulfurization (FGD) materials. While coal ash can be recycled for various beneficial uses, such as in concrete production and road construction, its storage poses significant environmental and health challenges. Improperly managed coal ash can leach toxic substances—including arsenic and lead—into groundwater, leading to serious health risks for humans and wildlife.
The methods for disposal are divided into dry and wet processes, with a notable proportion of coal ash stored in lagoons, which can become hazardous if containment systems fail. Historical incidents, such as the 2008 spill at the Tennessee Valley Authority's Kingston plant, have raised awareness and prompted calls for stricter regulatory oversight. The U.S. Environmental Protection Agency (EPA) has attempted to regulate the disposal of coal ash, implementing rules aimed at reducing environmental risks, though these regulations have faced legal challenges and revisions over the years. As of 2024, new regulations have been introduced to enhance safety measures surrounding coal ash storage and disposal, reflecting ongoing concerns about its impact on communities and ecosystems.
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Coal ash storage
Storing the ash produced by coal burning allows the material to be recycled in various uses, reducing waste. It can also help limit pollution by containing the environmental toxins found in coal ash. However, storage of coal ash presents several logistical challenges, and unregulated storage can create significant environmental and health hazards, especially through water pollution.
Overview
Coal is one of the most commonly used fossil fuels, including in power plants to generate electricity. The by-products of coal burning are called coal combustion by-products (CCBs) or coal ash.
Coal ash is generally divided into four types. Fly ash, the finest and most plentiful type of coal ash, forms from noncombustible matter in coal. Bottom ash, a coarse and granular material, comes from the bottom of coal-burning furnaces. Coal burned in a cyclone boiler produces a molten ash that, once cooled with water, forms a black material called boiler slag. (FGD) materials are the by-product of air-pollution-control systems called scrubbers that remove sulfur from the gases emitted by coal burning.
Recycling and disposal represent the two options for managing coal ash. All four types of coal ash have several beneficial uses. Fly ash can substitute for Portland cement in concrete and produce stronger, less porous, and cheaper forms of concrete. Bottom ash and boiler slag contribute to road base, asphalt paving, and material, and engineers have used boiler slag for blasting grit, roofing-shingle aggregate, and snow and ice control. Farmers use FGD gypsum as a soil amendment, and builders use it to make wallboard. By the twenty-first century, about one-third of coal ash and one-fourth of were recycled.
Methods of disposing of coal ash are divided into dry disposal, in which unwanted CCBs are transported to landfills, and wet disposal, in which coal ash is sluiced to storage lagoons. Combined coal ash in storage lagoons, known as ponded ash, accounts for approximately 30 percent of all disposed coal ash.
Coal ash often contains poisonous materials, such as arsenic, cadmium, chromium, lead, selenium, and other toxins that can cause cancer, liver damage, and neurological problems in humans and can kill fish and other wildlife. Toxins from coal ash storage lagoons can leach into groundwater. Studies by the US Environmental Protection Agency (EPA) have shown that coal ash dumps can significantly increase the of toxic metals in local drinking water. Additionally, coal ash used as fill-in material can ooze poisons into groundwater.
The retaining walls that enclose coal ash storage lagoons can also fail and produce environmental disasters. For example, on December 22, 2008, the ash enclosing a containment pond at the Tennessee Valley Authority’s Kingston Fossil coal-burning plant, near Harriman, Tennessee, broke. Approximately one billion gallons of coal flowed into tributaries of the Tennessee River, which supplies the drinking water for many people in parts of Alabama, Tennessee, and Kentucky. This incident contributed to growing pressure for stricter regulation of coal ash and coal ash storage in the United States.
Because coal ash can be reused, it was traditionally not classified as a in the United States, and its reuse was not subject to federal oversight. The EPA moved to address these issues in 2009, drafting a rule intended to prevent environmental damage from coal ash ponds by requiring such ponds to have synthetic liners and leachate collections systems and by phasing out leak-prone ash ponds. However, the draft rule was held up by the Office of Management and Budget. The EPA finally released its first regulation of coal ash disposal in 2015, but the rule faced legal challenges. Revisions were implemented in 2016, 2018, and 2020, mostly focusing on deadlines for coal facilities to implement the requirements. However, the 2020 rule also loosened limits on discharge of certain toxic metals in power plant waste. In 2024 the EPA released a new set of regulations targeting coal-burning power plants, including stricter controls around coal ash and ash ponds.
Bibliography
"Coal Ash (Coal Combustion Residuals)." United States Environmental Protection Agency, 20 May 2024, www.epa.gov/coalash. Accessed 22 May 2024.
"Disposal of Coal Combustion Residuals from Electric Utilities Rulemakings." United States Environmental Protection Agency, 9 May 2024, www.epa.gov/coalash/coal-ash-rule. Accessed 22 May 2024.
Freese, Barbara. Coal: A Human History. Cambridge, Mass.: Perseus, 2003.
Goodell, Jeff. Big Coal: The Dirty Secret Behind America’s Energy Future. New York: Houghton Mifflin, 2006.
Greb, Stephen F., et al. Coal and the Environment. Alexandria, Va.: American Geological Institute, 2006.