USGS Fact Sheet 076-01: Coal Combustion Products
Herein, we see that the United States Geological Survey, the USGS:
Welcome to the USGS - U.S. Geological Survey;
a bureau within the United States Department of the Interior, has studied the issue of Coal Utilization Byproducts, "CUBS"; performing more of a survey than anything else, and documented a number of current productive uses for what they, and others, refer to as Coal Combustion Products, "CCPS", a label which some prefer and which might, in fact, have more positive connotations.
In any case, should you be unfamiliar with the USGS, more can be learned via:
United States Geological Survey - Wikipedia, the free encyclopedia: "The United States Geological Survey (USGS) is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology, geography, geology, and hydrology.
The USGS is a fact-finding research organization with no regulatory responsibility.
A bureau of the United States Department of the Interior, it is that department's sole scientific agency.
The USGS was created by an act of Congress on March 3, 1879. It was charged with the "classification of the public lands, and examination of the geological structure, mineral resources, and products of the national domain." This task was driven by the need to inventory the vast lands added to the United States by the Louisiana Purchase in 1803 and the Mexican-American War in 1848."
We added the emphases in the above excerpt to make the point that the USGS has no particular political axe to grind, and are staffed, primarily, by down-to-earth, "just the facts, ma'am", geologists and other scientists.
And, we learn herein that they performed their own survey of the commercial and constructive uses in which the solid products arising from our essential use of Coal in the generation of electrical power can be, and are being, employed; and, reported the information succinctly, in a way that indicates how much genuine potential still exists for an even greater use of those products.
As seen in excerpts from the initial link to:
"U.S. Geological Survey; Fact Sheet 076-01: Coal Combustion Products
By: Rusty S. Kalyoncu and Donald W. Olson
The U.S. Geological Survey collaborates with the American Coal Ash Association in preparing its annual report on coal combustion products. This Fact Sheet answers questions about present and potential uses of coal combustion products.
What are coal combustion products?
Coal combustion products (CCP's) are the inorganic residues that remain after pulverized coal is burned. Coarse particles (bottom ash and boiler slag) settle to the bottom of the combustion chamber), and the fine portion is removed from the flue gas by electrostatic precipitators or other gas-scrubbing systems.
Because of concerns about air quality and acid rain, the U.S. Congress passed the Clean Air Act Amendments of 1990 (Public Law 101-549), which included stringent restrictions on sulfur oxide emissions. Most electric utilities in the Eastern and Midwestern States use bituminous coal having high sulfur contents of 2-3.5 percent.
In order to meet the emission standards, many utilities have installed flue-gas-desulfurization (FGD) equipment. The FGD products are included in coal combustion products. The components of CCP's are as follows: fly ash, 57 percent; FGD products, 24 percent; bottom ash, 16 percent; and boiler slag, 3 percent.
What is flue gas desulfurization?
Flue gas desulfurization is a chemical process to remove sulfur oxides from the flue gas at coal-burning powerplants. Many FGD methods have been developed to varying stages of applicability. Their goal is to chemically combine the sulfur gases released in coal combustion by reacting them with a sorbent, such as limestone (calcium carbonate,CaCO3), lime (calcium oxide, CaO), or ammonia (NH3). Of the FGD systems in the United States, 90 percent use limestone or lime as the sorbent. As the flue gas comes in contact with the slurry of calcium salts, sulfur dioxide (SO2) reacts with the calcium to form hydrous calcium sulfate (CaSO4 2H2O, gypsum).
What quantities of CCP's are generated?
About 100 million metric tons (Mt) of CCP's are generated annually by U.S. coal-burning electric utilities.
What are the uses for CCP's?
In the United States in 1999, approximately 30 percent of CCP's were used rather than discarded. The use of CCP's has increased over the years (to) just over 30 Mt in 1999. Fly ash is the most used CCP; in 1999, it made up about 64 percent of the total CCP's used. CCP's are used, in decreasing tonnage, in cement and concrete, structural fill, road bases, agriculture, and other applications. Components of CCP's have different chemical and physical properties that make them suitable for different applications:
- About 57 Mt of fly ash was produced in 1999, and about 19 Mt was used. The main uses were in concrete, structural fill, and waste stabilization.
(According to the Portland Cement Association, via:
Overview of the Cement Industry | Portland Cement Association (PCA); "Founded in 1916, the Portland Cement Association represents cement companies in the United States and Canada. It conducts market development, engineering, research, education, and public affairs programs. In 2008, the United States consumed 93.6 million metric tons of portland cement"'
we appear to make and use enough Portland Cement in the US, on a yearly basis, to use all, and more, of the Fly Ash we make each year, if we wanted to put our minds, and a little effort, to it.
Further, regarding the use of Coal Ash in "structural fill" and "road bases", see our report of:
West Virginia Coal Association | Fly Ash Facts for Engineers | Research & Development; concerning: "Fly Ash Facts for Highway Engineers; Report Number: FHWA-IF-03-019; 2003; Coal fly ash is a coal combustion product that has numerous applications in highway construction";
which explains those applications, and their potentials, in some detail.)
- About 15 Mt of bottom ash was produced in 1999, and about 5 Mt was used. The main uses were in structural fill, snow and ice control, road bases, and concrete.
- About 22 Mt of FGD (Flue Gas Desulfurization) material was produced in 1999, and about 4 Mt was used, mostly in wallboard manufacture.
(As we reported in:
West Virginia Coal Association | Pittsburgh Converts Coal Ash and Flue Gas into Cement | Research & Development; concerning: "United States Patent 5,766,339 - Producing Cement from a Flue Gas Desulfurization Waste; 1998; Assignee: Dravo Lime Company, Pittsburgh; Abstract: Cement is produced by forming a moist mixture of a flue gas desulfurization process waste product containing 80-95 percent by weight calcium sulfite hemihydrate and 5-20 percent by weight calcium sulfate hemihydrate, aluminum, iron, silica and carbon, agglomerating the moist mixture while drying the same to form a feedstock, and calcining the dry agglomerated feedstock in a rotary kiln. (And) wherein said source of aluminum and iron comprises fly ash";
"FGD material" could also be consumed, along with Fly Ash, in the making of cement.)
- About 2.6 Mt of boiler slag was produced in 1999, and about 2.1 Mt was used, predominantly in blasting grit and roofing applications.
What structural applications use fly ash?
Fly ash is added to cement and concrete and is used in many large-scale construction projects. Fly ash is a vital component in high-strength concrete in buildings that grace the skylines of major U.S. cities.
(Concerning the above, see:
US EPA Headquarters Housed in Coal Ash | Research & Development; wherein we're told, that "fly ash has been used in concrete since the 1930’s. Most notably, it has been used in several construction projects and prominent buildings, including the Ronald Reagan Government Office building, home to the Environmental Protection Agency (EPA) in Washington, D.C.".)
Fly ash concrete is used in the decks and piers of many highway bridges. Concrete pavements containing fly ash are very durable and cost effective. Between 1950 and 1970, concrete with fly ash contents as high as 50 percent was used in an estimated 100 major dam construction projects. In the construction of Hungry Horse Dam in 1953, for example, 120,000 metric tons of fly ash were used.
What are the benefits of using CCP's in all applications?
Use of CCP's offers significant environmental and economic benefits. Their long history of successful applications attests to the environmental acceptability of CCP's. WhenCCP's are used, natural resources can last longer and mining costs can be reduced. In 1999, the productive use of 30 Mt of CCP's saved $620 million in disposal costs and about 350 acres of landfill space and generated $150 million in sales, bringing total benefits to $770 million.
. . . in cement and concrete?
The largest use of CCP's (mostly fly ash) is in cement and concrete.
The CCP's displace portland cement and significantly reduce emissions of carbon dioxide (CO2), a greenhouse gas that may be associated with global warming. Portland cement manufacture requires the burning of fossil fuels and decomposition of carbonates, which release large amounts of carbon dioxide into the atmosphere. Use ofCCP's can potentially reduce carbon dioxide emissions by 10-14 Mt annually.
In 1998, 10.5 Mt of fly ash was used in cement and concrete, replacing 7 Mt of portland cement and thereby reducing carbon dioxide emissions by 7 Mt.
(As we've reported and explained, for one instance in:
West Virginia Coal Association | Coal Fly Ash Makes Concrete "Green" | Research & Development; concerning the report: "'How Does Pozzolanic Reaction Make Concrete 'Green'?'; 2011 World of Coal Ash (WOCA) Conference, May, 2011; Edwin R. Dunstan, Jr., PE; ERD Consultants, LLC, and Construction Materials Engineering Council; When Portland cement is produced, there is a significant amount of CO2 emitted from the calcination of limestone. If the amount of CO2 can be reduced a system can be considered to be more 'green'. (As we've previously documented, CO2 is emitted from the limestone during calcination via the reaction: CaCO3 + Heat = CaO + CO2. And, that is in addition to the CO2 emitted from whatever fuel might be combusted to generate the needed heat to calcine the CaCO3, i.e., limestone. Thus, any reduction in the amount of limestone utilized in the production of cement and concrete will result in significant reductions in the amount of Carbon Dioxide emitted by the various cement and concrete manufacturing industries.) Pozzolanic Reaction - Fly Ash: If a concrete mixture contains a pozzolan, less cement is required to obtain a specific strength. The National Ready Mix Concrete Association has recently developed a 'Sustainable Concrete Carbon Calculator'. As expected the primary source of CO2 is Portland cement. This calculator shows (that) a reduction in cement of 40% reduces carbon (emissions) by 37%";
there is nearly a one-to-one, by weight, reduction of CO2 emissions from a cement-making process when Coal Fly Ash is used to replace at least some of the limestone otherwise consumed. That is, each ton of limestone used in a cement-making process leads to the direct emission of nearly one ton of CO2 from the calcination of the limestone itself . If we could displace all of the limestone, the only CO2 emitted, for all practical purposes, would be from the source of energy used to heat the cement kiln, if that source relied on fossil fuel combustion.)
. . . in mine reclamation?
Large cavities left by underground mining make the ground susceptible to subsidence. Acid water draining from some underground mines reaches surface streams and lowers the pH, causing serious ecological damage. Demonstration projects have shown that injection of alkaline CCP's into abandoned mines can help control subsidence and abate acid mine drainage.
. . . in wallboard manufacture?
In 1999, about 2.8 Mt of synthetic gypsum produced as FGD material by electric utilities went into wallboard manufacture. The synthetic gypsum meets and often exceeds the specifications for wallboard manufacture. Some wallboard plants that will use 100 percent synthetic gypsum are being built and some have started production. In 1999, synthetic gypsum accounted for about 17 percent of the total gypsum used in wallboard manufacture, and this figure is expected to increase.
(Referring to the USGS's earlier statement, further above, that: "22 Mt of FGD (Flue Gas Desulfurization) material was produced in 1999, and about 4 Mt was used, mostly in wallboard manufacture", and, to the immediately above "synthetic gypsum accounted for about 17 percent of the total gypsum used in wallboard manufacture", if all wall board manufacture was converted to the use of FGD gypsum, that application would consume more than five times as much as it does currently, more than the actual total 1999 production of FGD synthetic gypsum.) .
How can cenospheres in fly ash be used?
Fly ash contains tiny, hollow, particulate ceramic spheres, typically ranging in diameter from 5 to 75 micrometers, which are called cenospheres. They exhibit some unique properties, such as high energy absorption, which results in protection against electromagnetic interference. They are used as fillers in composite materials, in insulations, and in paints. A potential application of cenospheres is as heat-reflecting coatings for rooftops. Widespread use of such coatings could lower average city temperatures in summer and reduce the need for air conditioning.
(See our report of:
West Virginia Coal Association | Wisconsin Recovers "Cenospheres" from Coal Fly Ash | Research & Development; concerning: "United States Patent 8,074,804 - Separation of Cenospheres from Fly Ash; 2011; Assignee: Wisconsin Electric Power Company, Milwaukee; Abstract: Methods for increasing the amount of cenospheres in a fly ash sample are disclosed. The cenospheres are obtained in a dry state by using air as the "fluid" media for separation. In one version, the invention is a two step process, that is, screen by size followed by density separation such as in a fluidizing vertical column by density. In another version of the invention, the separation by density is followed by screening by size. Additional cycles can improve purity as defined by concentration of cenospheres. This invention relates to a method in which the weight or volume percentage of cenospheres in a fly ash sample is increased preferably providing a material of nearly 100% cenospheres. The recovered cenospheres may be used to produce reinforced polymers, metals, ceramics, and other products".)
How can ammonium sulfate FGD's be used in agriculture?
A flue-gas-desulfurization method popular in Europe uses ammonia (NH3) as the sorbent; the FGD product is ammonium sulfate ((NH4)2SO4). Sulfate is the preferred form of sulfur readily assimilated by crops, and ammonium sulfate is the ideal sulfate compound for soil supplements because it also provides nitrogen from the ammonium. The use of ammonium sulfate in large-scale fertilizer formulations has been growing gradually. This growth provides a market for FGD products and could make FGDprocesses based on ammonia attractive alternatives to the processes based on lime and limestone.
The estimated worldwide annual shortage of almost 11 Mt of elemental sulfur for agricultural applications could be supplied by 45 Mt of ammonium sulfate. This much FGD product could result from 170,000 megawatt-hours (MWh) of electricity production if plants burned coal containing 2.5-3 percent sulfur. A relatively large powerplant generates 1,000 MWh of electricity per year. Thus, 170 large power plants burning high-sulfur coal and using FGD methods based on ammonia could produce the amount of ammonium sulfate needed for proper plant nutrition.
(See, for one example, our report of:
USDOE Converts Coal Exhaust into Fertilizer | Research & Development; concerning: "United States Patent 6,447,437 - Method for Reducing CO2, CO, NOx and SOx Emissions; 2002; Assignee: UT Battelle, LLC, Oak Ridge, TN; Abstract: Industrial combustion facilities are integrated with greenhouse gas-solidifying fertilizer production reactions so that CO2, CO, NOx, and SOx emissions can be converted prior to emission into carbonate-containing fertilizers, mainly NH4HCO3 and/or (NH2)2CO, plus a small fraction of NH4NO3 and (NH4)2SO4. Government Interests: This invention was made with United States Government support awarded by the Department of Energy to Lockheed Martin Energy Research Corporation, Contract No. DE-ACO5-96OR22464. The United States Government has certain rights in this invention. A method for reducing the emissions of industrial combustion facilities, comprising the steps of: collecting emissions from said industrial combustion facilities, reacting said emissions to form at least carbonate-containing fertilizers (including) NH4HCO3. The invention provides a method for reducing CO2, CO, NOx and SOx emissions by converting these emissions into useful fertilizers".)
What research is being done?
Recent environmental regulations have forced electric utilities to use low-NOx burners ("low-NOx" is a designation for burners that greatly reduce nitrogen oxide emissions). These burners leave some coal unburned, which leads to higher free carbon contents in fly ash and makes the ash unsuitable for use in cement and concrete applications. Many powerplants that previously could earn revenue from selling the fly ash have had to pay for its disposal. However, a novel technology, developed at Pennsylvania State University, can separate the unburned coal from the fly ash and may soon eliminate this problem. Moreover, the coal from the separation process is activated under steam at 850C and can be used in water and gas purification.
(We've noted other processes for removing such residual Carbon, as in:
West Virginia Coal Association | Virginia Converts Coal Ash to Cash | Research & Development; concerning the news report: "Dominion Recycling Center Turns Ash to Cash; The Virginia Pilot; November, 2006; It looks like a really big igloo, or maybe an indoor skating rink. But Dominion Virginia Power says the new, domed structure next to its Chesapeake power station will make money, create jobs and help the environment. The waterfront facility, on the Elizabeth River just south of the Gilmerton Bridge, is an ash recycling center - the first of its kind in Virginia, and just the fourth in the nation. The facility acts like a big oven. It bakes black, carbon-laden fly ash into a kinder, gentler and paler byproduct that can be sold and made into concrete, roof tiling and construction blocks, among other alternative uses";
and, will make further report on such and related technologies in the future.)
Utilities will continue to look for pollution-prevention technologies that will yield smaller quantities of FGD products that will be purer and have higher value than those presently produced. An example is the Basin Electric Cooperative's Dakota Gasification plant in Beulah, N. Dak., where a wet ammonia-based FGD process is used for SO2 removal in combustion of otherwise unsalable fuels derived from gasification of lignite. The resulting ammonium sulfate is sold and used as a sulfur blending stock in fertilizer production.
Research efforts to find new applications and increase the use of CCP's continue. Researchers at the University of Southern Illinois at Carbondale are working on the design for utility poles made of CCP's and organic binders. The researchers expect that the final product will be comparable to or even superior to the traditional creosote-coated wooden poles. In addition to eliminating the need for weatherproofing with creosote, which pollutes rainwater runoff, the CCP poles would be fireproof and termiteproof, would be cheaper to install, and would be more resistant to damage by humans and animals. It is estimated that 250,000 poles averaging 30-40 feet (9-12 meters) in height and another million poles 15-30 feet (4.5-9 meters) in height are used annually in the Midwestern United States alone. Replacing wooden poles with CCPpoles could double the use of fly ash while sparing millions of trees annually.
(We'll look into the Southern Illinois work, and try to make report of it on down the line. For now, concerning the combination of "CCP's and organic binders" in closely-related structural applications, we refer you to our earlier report of:
West Virginia Coal Association | Carbon Dioxide + Coal Fly Ash = Synthetic Lumber | Research & Development; concerning, in part: "US Patent Application 20080029925 - Filled Polymer Composite and Synthetic Building Material; 2008; Abstract: The invention relates to composite compositions having a matrix of polymer networks and dispersed phases of particulate or fibrous materials. The matrix is filled with a particulate phase, which can be selected from one or more of a variety of components, such as fly ash particles ... . A method of continuously forming a molded material comprising: forming a composite mixture in an extruder, wherein the composite mixture comprises: (polyurethane reaction components, and) about 45 to about 85 weight percent of inorganic particulate material ...; and a catalyst; extruding the mixture through a die; and molding the mixture into a shaped article. (And) wherein the shaped article is a building material (such as) lumber (or) roofing (or) siding. The invention relates to composite compositions having matrices of polymer networks and dispersed phases of particulate and/or fibrous materials, which have excellent mechanical properties, rendering them suitable for use in load bearing applications, such as in building materials. The composites are stable to weathering, can be molded and colored to desired functional and aesthetic characteristics, and are environmentally friendly, since they can make use of recycled particulate or fibrous materials as the dispersed phase ... which can be selected from one or more of a variety of components, such as fly ash.")
What are the barriers to CCP use?
There are many technical, economic, regulatory, and institutional barriers to increased use of CCP's. A lack of standards and guidelines for specific applications heads the list of technical barriers. Transportation costs lead the economic barriers, which limit the shipment of CCP's to within about a 50-mile (80-kilometer) radius of the powerplants.
The industry's ability to recycle CCP's may be limited by more restrictive environmental controls. In April 2000, the U.S. Environmental Protection Agency (EPA) stated that the use of CCP's does not warrant regulatory oversight but left the door open to stricter regulation of CCP's in the future. A few weeks later, theEPA nearly issued a ruling that would have classified CCP's as hazardous wastes under the Resource Conservation and Recovery Act (RCRA). In May 2000, theEPA reaffirmed its position that CCP's are nonhazardous.
Environmental regulation may also lead to the generation of lower quality, less usableCCP's. As mentioned above, the required use of low-NOx burners has resulted in fly ash having an unburned coal content that makes it unsuitable for concrete; until new technologies are applied, this fly ash must be used in other products or disposed of.
(Again, the above relates to the removal of residual Carbon, as noted even further above; which we will more adequately address in future reports.)
Other barriers to CCP use are the RCRA designation of CCP's as solid wastes, regardless of their composition, even when they are used as resources rather than disposed of; the lack of governmental incentive; and the lack of education among the user groups (engineers, contractors, and regulators).
With industry and government cooperation, steps toward increasing CCP use can include (1) establishing a research and development infrastructure to address the technical barriers to CCP use and to design innovative FGD methods and (2) providing objective scientific information.
What is the bottom line?
Coal combustion products have many economic and environmentally safe uses. For example, in construction, a metric ton of fly ash used in cement and concrete can save the equivalent of a barrel of oil and can reduce carbon dioxide releases that may affect global warming. The use of CCP's saves landfill space. CCP's can replace clay, sand, limestone, gravel, and natural gypsum, thus preserving the Nation's natural resources and helping to save energy and other costs associated with mining."
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The concluding statement, "CCP's can replace clay, sand, limestone, gravel, and natural gypsum", refers primarily to the use of CCP's in the making of cement and concrete, and wallboard, as discussed earlier on.
And, we think it important to note that even more energy would be, indirectly, conserved by substituting such reclaimed materials for those other, virgin products, i.e., "clay, sand", etc., since no effort or energy would have to be expended to extract those products from their natural deposits.
Some additional, indirect, reductions in CO2 emissions would be realized, thereby, as well.
In any case, it seems clear:
According to an entirely objective group of scientists, paid with public money and working in the public interest, the inorganic residua resulting from our essential use of Coal in the generation of genuinely economical electric power, all of it, every last single speck of it, can be seen and treated as a resource, a collection of raw materials that can be completely consumed and utilized in the manufacture of a range of needed and used commodity products and raw materials, all of which raw materials would otherwise, as they do now, require the expenditure of energy and the disruption of our natural environment to be obtained.
Coal Combustion Products are a valuable resource.
To allow those products to be treated as some sort of "waste" which we must, at great expense, somehow dispose of in a way satisfactory to the rabid critics of the Coal industry, whose motives, now, especially, in light of recent news reports concerning the funding of anti-Coal campaigns by competing energy resources, is a deceptive crime against, a fraud being perpetrated on, not only the citizens of United States Coal Country, but, against both the economy and the environment of the entire United States of America.