Coal Combustion Products: Trash or Treasure?

Issue 7 and Volume 110.

Coal combustion by products can be a valuable resource to various industries.

By Teresa Hansen, Associate Editor

One man’s trash is another man’s treasure. Although the by products created during the coal combustion process are not exactly trash, coal-fired power plant owners must find either a viable use for them or a place for their disposal. In many cases, these by products can be used by other industries, making them at least a valuable resource. The American Coal Ash Association (ACAA), an industry association created to promote the beneficial uses of coal combustion by products-or what ACAA calls coal combustion products (CCPs)-says that CCPs are the fourth largest-volume mineral resource produced in the United States.

Today, more than half the electricity produced in the United States comes from coal-fired generating plants. As electricity demand increases, coal-fired generation is expected to increase with it. The Energy Information Administration (EIA) predicts that coal-fired electricity generation will rise about 1.5 percent per year through 2025. These statistics make clear the fact that CCP production will increase.

The Real Scoop

Annually, ACAA collects CCP data from electric generators (see sidebar on page 72). Its latest report estimates that 122.5 million tons of CCPs were produced in 2004. These figures are industry-wide estimates based on voluntary data received from electricity generators, and represent nearly 500 coal-fired power generating facilities. ACAA points out that total CCP production can vary from year-to-year based on total coal burned, type of coal burned, ash content and the extent of flue gas emission controls used.

ACAA’s data show that approximately 49.1 million tons, just more than 40 percent, of the CCPs produced were used, primarily in building and construction. This was an increase from the 46.6 million tons used in 2003. ACAA attributes the increase to wider acceptance of CCPs in the building and construction industries and says the increases are “testimonials to the environmental, technical and economic advantages that these materials present where each ton of CCPs used is one less ton disposed of.”

The Great Plains Synfuels Plant is the only commercial-scale coal gasification plant in the United States that manufactures natural gas. Photo courtesy of Basin Electric Power Cooperative. Click here to enlarge image

Almost all utilities are interested in selling as much by product as possible, says David Goss, ACAA’s executive director. They are interested not only because it is economical, but because it is an environmentally responsible thing to do. Besides saving space in landfills, any product that is used offsets the natural resources that must be mined. Those natural resources are thus available for other uses.

According to the Coal Ash Fact Sheet, published by the American Coal Council and the ACAA, for each ton of fly ash used in place of a ton of cement, one ton of CO2 emissions are displaced. That equals about 10 million tons of displaced CO2 annually, another good reason to find markets for CCPs, Goss says.

Fly ash is predominantly used as a substitute for Portland cement and continues to be the most widely used CCP. ACAA’s survey found that in 2004, 70.8 million tons of fly ash was produced by electric generating facilities. About 14.1 million tons was used as a substitute for the cement. Fly ash enhances concrete’s strength and durability and typically costs less than Portland cement. Another 14 million tons of fly ash was used for other purposes, mostly construction and building, related activities (Table 1, page 68). This increase is consistent with the country’s high construction demand.

Approximately 17.2 million tons of bottom ash (granular, gravel-like material) was produced in 2004, according to ACAA. Less than half, just more than 47 percent or about 8.2 million tons, of the bottom ash produced in 2004 was used. It is used primarily as structural fill, embankments and paved road bases.

The synthetic gypsum produced from the flue gas desulphurization (FGD) process is another common CCP. According to Goss, 27 percent of the wallboard made in the United States contains synthetic gypsum produced by FGD systems. Because the amount of synthetic gypsum produced by coal-fired power plants is directly tied to the sulfur content of the coal and the resulting SO2 scrubbed from the flue gas, synthetic gypsum production will likely increase as more coal plants clean their flue gas streams and/or as older coal plants are replaced. ACAA’s survey found that in 2004 almost 12 million tons of synthetic gypsum was produced. Of that, more then 9 million tons, 75 percent, was used.

Putting Pen to Paper

While most coal-fired power plant owners are interested in selling their CCPs, the economics of CCP commerce can vary depending on where a power plant is located.

“Disposal costs and CCP prices are different from region to region, much of it depends on how much land is available for refuse,” Goss explains. For example, in states such as Colorado or Wyoming, where land is generally more available for CCP disposal, it can cost $6 to $15 a ton to dispose of fly ash. The lower cost reflects the cost if the plant owner also owns the landfill. The higher cost is more typical if the plant owner uses a municipal, county or private landfill. In a crowded urban area such as New York City, by contrast, where landfill space is at a premium and wastes are transported by rail to other states, disposal costs can be as high as $100 a ton. In other metropolitan areas, costs may be between $30 and $50 a ton.

Thus, where disposal costs are high power plant operators will likely find it economically advantageous to sell CCPs simply to avoid disposal fees.

In addition to avoiding disposal fees, finding buyers for CCPs can create new revenue streams. “Prices for concrete quality fly ash are highly dependent on market conditions and material availability,” Goss says. “In Colorado, the going price for a ton of concrete quality fly ash is about $35 to $45. In New York City, the price is $60 to $65 per ton.”

To illustrate, consider a hypothetical plant that uses 8 million tons of coal a year at a cost of $30 a ton. This amounts to $240 million a year for fuel cost. Now assume that 8 million tons of fuel equates to about 800,000 tons of coal ash. Of that, 80 percent-or about 640,000 tons-is fly ash. If the cost to dispose of the fly ash is $30 a ton, the utility can figure on spending more than $19 million a year in disposal fees. Looked at a different way, at a price of $35 a ton for fly ash, the utility could be losing more than $22 million annually in additional revenue. “This equates to more than $41 million in total costs and lost revenue,” Goss says.

Much of the fly ash from Basin Electric Power Cooperative’s Laramie River Station produced concrete for Denver International Airport. Photo courtesy of Chris Carter, DIA. Click here to enlarge image

To realize the maximum revenue in this example, the power plant owner must have a buyer for the plant’s fly ash and thus avoid all disposal fees. In the real world, this isn’t likely to happen. Instead, the power plant owner would likely have a buyer for only a portion of the fly ash and other CCPs.

Fishing for Markets

Basin Electric Power Cooperative owns three coal-fired generating stations, one in Wyoming and two in North Dakota. At one time it was quite successful at selling its fly ash. “During construction of the Denver airport, virtually all the fly ash produced at our Laramie River Station in Wheatland, Wyo., was used to produce concrete for the airport,” says Daryl Hill, Basin Electric’s news media coordinator. “However, fly ash sales from our power plants have tapered off considerably in the past few years. We still sell a little fly ash from Laramie River Station to a local cement company, but fly ash sales from our Antelope Valley Station (near Beulah, N.D.) are down to zero. Although some is used by the nearby coal mine for road stabilization.” Hill believes the minimal fly ash sales are the result of a market surplus of the by product. However, he reports that at the Leland Olds Station (Stanton, N.D.) some bottom ash is sold for various industrial uses.

A sometimes overlooked by product from coal-fired power plants is heat, or more precisely, hot water. There was a time at the Antelope Valley Station where a fish farm used hot water to raise tilapia, a tropical fish, Hill says. Hot water from the plant’s condensers was diverted to the fish farm before it went to the cooling towers.

Click here to enlarge image

“While the technology that allowed for utilization of the ‘waste heat’ worked well, the economics didn’t,” Hill says. Revenues did not meet expectations and the fish farm closed. Hill says that the operation is unlikely to be restarted.

Although Basin Electric doesn’t sell a large volume of CCPs from its coal-fired power plants, its subsidiary, Dakota Gasification Co., is seeing somewhat more success marketing and selling by products from its Great Plains Synfuels Plant. The plant is the only commercial-scale coal gasification plant in the United States that manufactures natural gas. It is located adjacent to the Antelope Valley Station near the Freedom mine, one of the nation’s largest coal (lignite) mines.

The plant consumes about 18,000 tons of lignite daily and produces about 160 million cubic feet of natural gas that is distributed mainly in the eastern United States. The syngas plant produces many by products that are sold in the United States and worldwide. Those products are:

  • Anhydrous ammonia – an agricultural fertilizer.
  • Ammonium sulfate – another agriculture fertilizer sold under the trademark name DakSul 45. DakSul 45 is the by product of the synfuels plant’s scrubber, which removes sulfur dioxide (SO2) emission. The reagent used to react with SO2 is anhydrous ammonia. The resulting chemical reaction is ammonium sulfate which is then processed to a granular product.
  • Crude cresylic acids – used to produce other products, such as wire enamel solvents, adhesives, phenolic and epoxy resins.
  • Phenol – used to manufacture a variety of phenolic resins in wood products and foundry molds.
  • Krypton/xenon – rare gases obtained from the synfuel plant’s oxygen plant. Krypton and xenon are generally used for high-intensity lighting and some laser applications.
  • Carbon dioxide -by far the most talked-about byproduct produced at the synfuels plant. Appoximately 110 million cubic feet per day are shipped from the plant to two oilfields 200 miles away in Saskatchewan, Canada, where it is used for enhanced oil recovery. When a project expansion is completed later this year, up to 160 million cubic feet per day will be delivered.
  • Tar oils – primarily a boiler fuel in the plant. The plant’s boilers produce steam which is used in the gasifier vessels to gasify coal.
  • Liquid nitrogen – used as cryogenic storage medium, as well as oil additive for fracturing and foam agent.

According to Hill, a portion of the natural gas produced at the plant is used to make some of the by products. “One of the main ‘ingredients’ required to manufacture anhydrous ammonia is natural gas. Over the past several years, an econometric model has been developed that takes into account the selling price of natural gas and anhydrous ammonia,” Hill says. “The model provides an analysis of what creates the most revenue: selling natural gas or selling anhydrous ammonia. We use this model to evaluate the economics of using the synthesis gas to produce either ammonia or synthetic natural gas. Depending on the economics, we adjust the production of ammonia accordingly. Some of the anhydrous ammonia is used to produce the ammonia sulfate.”

Dakota Gasification’s reasons for developing and finding markets for the syngas plant’s by products were twofold: to offset by-product remediation costs and to provide an additional revenue source.

“The primary reason for developing the by products was to provide a revenue-stream diversity that wasn’t entirely dependent on natural gas sales,” Hill says. “There was a time in the plant’s history when prices for natural gas were far below production costs. During those times the revenues produced from by product sales did help, but did not entirely provide financial stability.”

Although the Great Plains Synfuels Plant is one of a kind, rising natural gas prices are creating a renewed interest in the idea of turning coal into natural gas. If such talk leads to actual new synfuel plant construction, Dakota Gasification’s marketing program could be a model for future facilities.

In the meantime, ACAA’s Goss believes markets exist for coal-fired power plants’ CCPs. His organization is ready to help power plant owners and industries manage CCPs and develop markets.

“ACAA’s goal is to educate people, including politicians and government officials, about CCPs and the technology that is available to make them into useful products,” Goss says.

Goss and all ACAA members (see sidebar on page 68) share a common goal of using CCPs as valuable products to support environmental stewardship, reduce disposal activities, enhance revenue and reduce liabilities. As the amount of CCPs being produced increases, this goal will become even more important.

The American Coal Ash Association

The American Coal Ash Association (ACAA) is a not-for profit organization that promotes the beneficial use of coal combustion products (CCPs), such as fly ash, bottom ash, boiler slag, flue gas desulfurization materials and other similar materials. CCPs have a myriad of uses that allow the substitution of CCPs for natural or manufactured materials in many processes and applications.

The organization’s mission is to advance the management and use of CCPs in ways that are technically sound, commercially competitive and environmentally safe. ACAA and its members work to gain the recognition and acceptance of specifiers, designers, contractors, legislators, regulators and others for CCPs on par with competing engineering and manufactured materials. ACAA’s work in support of its mission also serves the entire “CCP industry.” ACAA members represent the entire CCP industry and include coal-burning electric utilities, coal companies, allied trade groups and others with commercial academic, research and other CCP management interests. The members include:

A.W. Oakes & Sons Inc.
ACTIVATION Resources International LLC
ADA Environmental Solutions Inc.
AES Puerto Rico
Alliant Energy
American Energy Fuels and Services Co. (AFS)
American Electric Power
Boral Material Technologies Inc. (BMTI)
Charah Inc.
Cinergy Corp.
Combustion Products Management
Cumberland Elkhorn Coal & Coke
W. Lee Daniels, Professor
Dairyland Power Cooperative
Detroit Edison
Duke Energy
Dynergy Inc.
Ecologica Carmelo Inc.
EMC Development AB
FlyAsh Direct
Freeman Energy Corp.
Fremont Department of Utilities
Full Circle Solutions Inc.
GAI Consultants Inc.
Gerard Gambs, P.E., Consulting Engineer
Dean Golden, Consulting, Civil Engineer
Golder Associates Inc.
Great River Energy
Headwaters Resources
Holcim (US) Inc.
Indianapolis Power & Light Co.
Kansas City Power & Light Co.
Korea Coal Ash Recycling Association
Lafarge North America
LB Industrial Systems LLC
Lehigh Cement Co.
LG&E Energy LLC
LMS Environmental Contracting Inc.
Lower Colorado River Authority
McDonald Farms Enterprises Inc.
Mineral Resource Technologies
Mirant Mid-Atlantic
Dr. Barzin Bobasher, Ph.D, P.E., Assoc. Professor
Montana-Dakota Utilities Co.
Dr. Ishwar P.Murarka, Consultant
Muscatine Power and Water
Tarun R. Naik, Ph.D., P.E.
National Gypsum Co.
Nebraska Ash Co.
Nebraska Public Power District (NPPD)
Pittsburgh Mineral & Environmental Technology Inc.
Pozzi-Tech Inc.
PPL Generation LLC
Progress Energy
Public Service Enterprise Group (PSEG)
Public Service of New Hampshire
Rio Bravo, Constellation Energy
Salt River Materials Group
Salt River Project (SRP)
Santee Cooper
Don Saylak, Ph.D., P.E.
Seminole Electric Cooperative Inc.
Separation Technologies LLC
South Carolina Electric & Gas Co. Inc.
Southern Company Generation
Southern Illinois Power Cooperative
Southern Illinois University
Sphere Services Inc.
Sunflower Electric Power Corp.
Synthetic Materials (SYNMAT)
Temple-Inland Inc.
Tennessee Valley Authority
Tephra Resources LLC
Ohio State University
Coal Combustion Products Extension Program
The SEFA Group
Trans-Ash Inc.
University of Kentucky –
Center for Applied Energy Research
University of North Dakota
Energy & Environmental Research Center
U.S. Gypsum Co.
We Energies
Western Greenbrier Co-Generation LLC
Western Research Institute-
University of Wyoming
West Virginia Water Research Institute-
West Virginia University
Xcel Energy

More information about ACAA is available at