Civil and Environmental Engineering and Geodetic Science
Civil and Environmental Engineering and Geodetic Science
Ohio Agricultural Research and Development Center
Waste Management Section
American Electric Power
Food, Agricultural and Biological Engineering
More than half of the electricity generated in the United States is produced by coal-fired facilities. The Clean Air Act Amendments of 1990 require many utilities, especially those in the Midwest, which burn high-sulfur bituminous coal, to reduce sulfur dioxide emissions. This has resulted in the generation of large amounts of coal combustion products (CCPs). These products include fly ash, bottom ash, boiler slag, and flue gas desulfurization (FGD) material (see Table 1). In 1996 approximately 800 million tons of coal were burned in the United States to produce electricity. This led to the generation of over 90 million tons of CCPs. The total tonnage of CCPs generated surpassed Portland cement and iron ore production in the United States and ranked behind only crushed stone, sand, and gravel among non-fuel mineral sources.
Figure 1 shows the amount of each type of CCP generated in 1996 and the amount that was utilized. Overall, one-fourth of the CCPs generated were utilized while the rest were disposed of mainly by landfilling. Only 7% of the FGD material generated in the United States was utilized. With Phase 2 of the Clean Air Act Amendments of 1990 going into effect in the year 2000, the amount of FGD material produced in the United States may increase by an order of magnitude to almost 200 million tons, thus exceeding the production of all other CCPs (Kalyoncu, 1996). Increasingly stringent emission requirements will result in a further increase in the production of CCPs as long as electric utility industries continue to burn coal to produce electricity.
Figure 1. Coal combustion product production and use in the United States in 1996 (Source: American Coal Ash Association)
|Table 1. Types of coal combustion products and their characteristics|
|CCP type||Characteristics||Texture||Amount typically generated
per ton of coal burned (lbs.)
|Fly ash||Non-combustible particulate matter removed from stack gases||Powdery, silt-like||160||Si, Al, Fe, Ca|
|Bottom ash||Material collected in dry bottom boilers, heavier than fly ash||Sand-like||40||Si, Al, Fe, Ca|
|Boiler slag||Material collected in wet bottom boilers or cyclone units||Glassy, angular particles||100||Si, Al, Fe, Ca|
|FGD material||Solid/semi-solid material obtained from flue gas scrubbers||Fine to coarse (dry or wet)||350||Ca, S, Si, Fe, Al*|
|* Fixated FGD material is a mixture of filter cake (Ca, S), fly ash (Si, Fe, Al), lime, and water. Major constituents of gypsum quality FGD material are Ca and S.|
Nearly 90% of the electricity produced in Ohio is generated from burning of coal, and the state generates about 12% (11.6 million tons) of all CCPs produced in the United States. These products, produced in large quantities, have traditionally been disposed of in expensive, non-productive landfills. Many of these products are separated from other product streams. If treated and applied correctly, these materials have versatile properties that make them suitable raw materials for many uses ranging from highway/civil engineering applications, mineland reclamation, to agricultural applications. The recycling of CCPs as raw materials in applications that are environmentally sound, technically safe, and commercially competitive should lead to a reduction in the practice of landfilling these raw materials. Their continued utilization will lead to: 1) a decrease in the need for landfill space, 2) conservation of the natural resources of the state, 3) reduction in the cost of producing electricity, 4) lower electricity cost for consumers, and 5) substantial savings for end-users of CCPs.
Leachate tests conducted on CCPs have shown that the leachate from these materials generally meets the national primary drinking water standards. Fly ash, bottom ash, boiler slag, and FGD material are being used today as raw materials in many different application technologies. Table 2 shows the different uses for CCPs.
|Table 2. Uses of coal combustion products|
|CCP Type||Potential areas of major use|
|Fly ash||Cement replacement in concrete/grout, structural fill, flowable fill, waste stabilization, surface mine reclamation, soil stabilization, road base, mineral filler|
|Bottom ash||Concrete block, road sub-base, snow and ice control, structural fill, waste stabilization, pipe bedding, cement manufacture|
|Boiler slag||Blasting grit, roofing granules, snow and ice control, mineral filler, construction backfill, water filtration, drainage media|
|FGD material||Wallboard, stabilized road base/sub-base, structural fill, surface mine reclamation, underground mine injection, livestock pad, low permeability liner, synthetic gypsum raw material, liming substitute, soil conditioning, synthetic aggregate, sludge stabilization|
When treated and applied correctly, coal combustion products can be put to multiple productive uses in civil engineering, mine reclamation, and agricultural applications. The use of these materials in ways that are technically sound, environmentally benign, and commercially competitive can result in significant savings for CCP end-users, coal-fired facilities, and the people of the state of Ohio.
A pilot Extension program is currently in place at The Ohio State University to move CCP technologies and processes from the research and development phases into the marketplace. More information on the use of CCPs can be obtained from the Internet web site http://ccpohio.eng.ohio-state.edu or by contacting the Extension program coordinator:
Dr. Tarunjit S. Butalia, P.E.
Research Specialist: Coal Combustion Products Coordinator
Department of Civil and Environmental Engineering and Geodetic Science
The Ohio State University
470 Hitchcock Hall, 2070 Neil Avenue, Columbus, OH 43210-1275
Phone: 614/688-3408; Fax: 614/292-3780;
Coal Combustion Byproducts. 1996. R. Kalyoncu. US Geological Survey-Minerals Information.
Coal Combustion Products (CCPs) Production and Use: Current Trends. 1997. B. Stewart. Proceedings of the 1997 International Ash Utilization Symposium, Lexington, Kentucky, October 20-22. Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky.
Land Application Uses of Dry FGD By-Products: Phase 1 Report. 1995. R. Stehouwer, W. Dick, J. Bigham, L. Forster, F. Hitzhusen, E. McCoy, S. Traina, and W. Wolfe. Electric Power Research Institute, Report # EPRI TR-105264. Electric Power Research Institute, Palo Alto, California.
Land Application Uses of Dry FGD By-Products: Phase 2 Report. 1998. R. Stehouwer, W. Dick, J. Bigham, L. Forster, F. Hitzhusen, E. McCoy, S. Traina, and W. Wolfe. Electric Power Research Institute, Report # EPRI TR-109652. Electric Power Research Institute, Palo Alto, California.
Land Application Uses of Dry FGD By-Products: Phase 3 Report. May 1998. W. Dick, J. Bigham, L. Forster, F. Hitzhusen, R. Lal, R. Stehouwer, S. Traina, and W. Wolfe. The Ohio State University, Final Technical Report, EPRI Project RP2796-02. The Ohio State University, Columbus, Ohio.
Utilization of Coal Combustion Products in Ohio. 1998. T.S. Butalia, and W. Wolfe. Proceedings of the 23rd International Technical Conference on Coal Utilization and Fuel Systems, Clearwater, Florida, March 9-13, Coal and Slurry Technology Association, Washington, D.C.
This publication was produced through a cooperative effort between Ohio State University Extension and the College of Engineering at The Ohio State University. The technical information presented in this publication was collected through the financial support of Ohio Department of Development's Ohio Coal Development Office, US Department of Energy's Federal Energy Technology Center, American Electric Power Company, Cinergy, FirstEnergy, and Dravo Lime Company. American Coal Ash Association-National and Ohio Chapter, Ohio Farm Bureau Federation, Ohio Dairy Farmers Association, and Ohio Cattlemen's Association provided additional support.
The authors express their appreciation to the following reviewers: Greg Sanders (Ohio EPA); Michael Monnin, Robert Keen, Robert Hendershot (USDA-NRCS); Kevin Elder (ODNR); Donald Clark (Ohio Department of Development); William Aljoe (US Department of Energy's Federal Energy Technology Center); David White (Ohio Farm Bureau Federation); Stephen Boyles, Phil Rzewincki, Hal Walker, Earl Whitlach, Don Eckert, Paul Golden, Brian Strobel, Doug Clevenger (The Ohio State University); Robert Brown (Ohio Coal Development Office); Howard Humphrey, Shan Mafi (American Electric Power); Michael Bates (FirstEnergy); Joel Beeghly (Dravo Lime Company); Jack Cline (Hocking College); Michael Schroeder (American Coal Ash Association-Ohio Chapter). Copies of this fact sheet were also sent to the following agencies for review: Ohio Department of Agriculture, Ohio State University Extension District Offices, Cinergy, Ohio Cattlemen's Association, Ohio Dairy Farmers Federation, Ohio Rural Development Partnership, Ohio Pork Producers Council.
For more information on the use of CCPs, please visit the "CCPOhio" web page at: http://ccpohio.eng.ohio-state.edu
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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