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Solid Waste Coal Ash Management

Coal Combustion Product Management at Duke Energy

Coal Combustion Product Management at Duke Energy

Coal Combustion Products (CCPs) are created when power plants burn coal to generate electricity for customers, or through the use of emission-control technologies. CCPs include coal ash, synthetic gypsum - also referred to as flue gas desulfurization (FGD) gypsum – FGD solids, and cenospheres.

Some Duke Energy CCPs are reused in a number of engineered products including cement, concrete, road bases, wallboard and even bowling balls. This benefits the environment, the energy industry and the products themselves. CCPs that are not reused are placed in landfills or stored in on-site ponds.

Ash Ponds

The December 2008 structural failure of a coal ash storage pond at the Tennessee Valley Authority’s (TVA) Kingston electric generating facility in Eastern Tennessee generated increased interest from numerous stakeholders regarding the electric power industry’s practice of storing coal ash in ponds. This event raised questions about the structural integrity of coal ash storage ponds across the country and the potential environmental and public health implications from storing coal ash in ponds.

Duke Energy is committed to the continued management of its coal combustion products in a manner that protects human health and the environment.

  • We have installed groundwater-monitoring wells around all of our active ash ponds, and we take samples multiple times a year. We will work with state agencies to develop action plans based upon the results, if needed.
  • We own the majority of land around our active facilities; therefore, very few public or private groundwater wells or residents are located near our ash ponds.

Most of the constituents we monitor are nontoxic and do not have health-based drinking water standards. For example, we monitor manganese because of an aesthetics-based secondary drinking water standard for the smell and color of the water. There is no drinking water standard established for some constituents, such as boron.

Frequently Asked Questions

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What is Coal Ash?

Coal ash is the unburned material that remains after coal is burned to generate electricity. Coal ash includes bottom ash, boiler slag and fly ash. Bottom ash is generally gray or black with the consistency of coarse sand. Boiler slag is black and angular with a glassy appearance. Bottom ash and boiler slag settle to the bottom of the boiler during combustion, where they are collected and transported – usually by water in piping – to an on-site storage facility.

Fly ash is a fine, lightweight powder. It is usually tan to dark gray in color and similar in consistency to talcum powder. Fly ash exits the boiler as part of the exhaust gas and is captured in a mechanical collection device to prevent its release into the air. Then, it is transported by either water (in piping) or air (in ductwork) to an on-site storage facility.

Coal ash, made up mostly of silica, iron, calcium and aluminum, is similar in composition to many of the rocks in the earth’s crust. Coal ash can also contain trace amounts of other substances that occur naturally in coal, such as arsenic, cadmium, lead, mercury and selenium. These substances are also found naturally in soil and rock.

What are Synthetic Gypsum and Flue Gas Desulfurization Solids?

When coal is burned, the sulfur that is present naturally within it is converted to sulfur dioxide (SO2). Many of Duke Energy's power plants employ what is commonly referred to as a scrubber, which is shorthand for flue gas desulfurization equipment or FGD, to remove the SO2 from the exhaust gas and prevent its release into the air. Synthetic gypsum and flue gas desulfurization solids are both byproducts of the scrubbing process. There are several different types of scrubbing processes, and the type of scrubbing process determines of the type of FGD solids produced.

Most of Duke Energy's scrubbers are produce synthetic gypsum. The synthetic gypsum that is produced in a scrubber is nearly identical to the mineral gypsum found in rock formations around the world. In fact, it's chemically more pure than mineral gypsum.

How are coal combustion products managed at Duke Energy’s coal-fired power plants?

The CCPs that are produced at Duke Energy’s coal-fired power plants that are not sold or not otherwise beneficially reused are managed in the following ways.

Coal-Fired Power Plant Location Bottom Ash and Boiler Slag Fly Ash Synthetic Gypsum and FGD Solids
Allen Gaston County, N.C. Wet Handling Dry Handling Landfill
Asheville Buncombe County, N.C. Wet Handling Wet Handling Landfill
Beckjord Clermont County, Ohio Wet Handling Wet and Dry Handling None Produced
Belews Creek Stokes County, N.C. Wet Handling Dry Handling Landfill
Buck Rowan County, N.C. Wet Handling Wet Handling None Produced
Cape Fear Chatham County, N.C. Wet Handling Wet Handling None Produced
Cayuga Vermillion County, Ind. Wet Handling Wet Handling Landfill
Cliffside Cleveland/Rutherford Counties, N.C. Wet Handling Wet and Dry Handling None Produced
Crystal River Citrus County, Fla. Dry Handling Dry Handling Landfill
Dan River Rockingham County, N.C. Wet Handling Wet Handling None Produced
East Bend Boone County, Ky. Wet Handling Dry Handling Landfill
Edwardsport Knox County, Ind. Wet Handling Wet Handling None Produced
Gallagher Floyd County, Ind. Wet Handling Dry Handling None Produced
Gibson Gibson County, Ind. Wet Handling Wet Handling Landfill
H. F. Lee Wayne County, N.C. Wet Handling Wet handling None Produced
Lee Anderson County, S.C. Wet Handling Wet Handling None Produced
Marshall Catawba County, N.C. Wet Handling Dry Handling Landfill
Mayo Person County, N.C. Wet Handling Dry Handling Landfill
Miami Fort Hamilton County, Ohio Wet Handling Wet and Dry Handling Landfill
Riverbend Gaston County, N.C. Wet Handling Wet Handling None Produced
Robinson Darlington County, S.C. Wet Handling Dry Handling None Produced
Roxboro Person County, N.C. Wet Handling Dry Handling Landfill
Sutton New Hanover County, N.C. Wet Handling Wet Handling None Produced
Wabash River Vigo County, Ind. Wet Handling Wet and Dry Handling None Produced
Zimmer Clermont County, Ohio Dry Handling Dry Handling Landfill