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Besides the power plant fly ash which was used in the concrete, this unique house contains aluminum processed from beverage cans picked off a Florida beach, glass bottles from California parks, old newspapers from New Jersey, scrap fibers from North Carolina carpet plants, worn-out tires from Mississippi, fibers from a municipal waste separation plant in Ohio, wood scraps from mills in the area, steel mill furnace slag, and recycled copper and scrap cast iron.

Faced with increasingly stringent regulations for better control of environmental problems, the coal-burning electric utilities have discovered they can turn the ash fallout from the energy production cycle into profitable by-products. Ash disposal by the traditional method (dumping) is becoming less and less satisfactory

However, the utilities face an even more imposing problem as they move to comply with clean air emission control standards by mid-1975 and that is what to do with lime sludges that will result from the installation of scrubbing systems to remove sulphur dioxide from stack emissions. This gray, toothpaste-like residue could be even more of an ecological problem than the ashes, and technology presently available to cope with this situation is scarce. Aside from individual efforts no real impetus was employed to market power plant ash until the creation of the National Ash Association by a group of public utility, coal, and coal-related industries in 1968. Today, a host of interests-private, governmental, and academic-are concerned with ash production, sales, utilization, and research.

The many outlets for ash, however, consume only about 16 percent of the total amount being produced. In 1973, total ash production reached an all-time high approaching 50 million tons, and this figure is expected to be exceeded before 1980. It is clear new markets must be found, and there is ample evidence they do exist.

In terms of production, coal ash is the seventh most abundant solid mineral according to figures compiled for the U.S. Department of Interior's 1972 Minerals Yearbook. Ash ranks behind sand gravel, stone, coal, iron, portland cement, and clays. (See Table 1.) Thus, it is also appropriate to note that the General Assembly of Maryland, in an historic action, passed legislation in April 1974 classifying power plant ash as a natural resource and providing for the material to be stockpiled so it can be fully recovered. Other states are said to be considering similar legislation.

TABLE I.-Production of Minerals and Solid Mineral Fuels

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Source: Mineral Yearbook, vol. I-II, Metals, Minerals, and Fuels, U.S. Department of the Interior, 1972.

Most of the ash production is centered east of the Mississippi River where the bulk of the fossil fuel is now mined. In 1973, almost 90 percent of the ash or about 40 million tons were collected there. And interestingly enough, approximately 50 percent of the total is available from twelve utility companies.

Considering all factors with regard to advancement in emission controls, nuclear power, and competition from oil and gas, it is estimated the 1980 consumption of coal will exceed 480 million tons with a resultant ash production of 52 million tons. (See Table 2). However, the characteristics of the ash may vary substantially from what they are today depending on the ash content of the lignite and low-sulphur coals that are being blended with the so-called highsulphur fuels and the types of processes employed to remove SO2 gases. The sup

plemental recycling of pulverized solid wastes into boiler furnaces could also alter the ash picture in some areas.

Table II. Coal consumption and
total ash production by U.S. elec-
tric utilities

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Additionally, the technology for new sources of energy production such as geothermal, MHD systems, breeder reactors, and solar systems do not appear likely before the turn of the century. Another vital factor to remember is that the ash from the coal-fired generating stations will continue to be available whether or not the sheiks of Kuwait turn off the oil valves again. This is particularly true of the mine-mouth stations within Appalachia.

Not all ash is the same. Variances in equipment, burning techniques, and coal are the major factors responsible for the differences in their chemical and physical composition. Generally speaking there are two kinds of ash: fly ash, which is the powdery particulate collected from the flue gases in the stacks, and the bottom ash or boiler slag that drops to the furnace floor during the burning process.

Currently these ashes are being utilized in a number of ways including the manufacture of cement, in concrete and concrete by-products construction or

structural fills, road base and soil stabilization; in production of lightweight aggregate, mineral fillers for asphaltic pavement, oil well grouting, foundry cores, for sand-blasting grit, and ice control. The ash industry has no intention of re-inventing the wheel, but a back-to-the-earth recycling concept offers great potential for volume use of the material in environmentally oriented applications. As joint partners with the coal industry many utilities look upon the use of ash in terms of a closed fuel cycle in which coal is purchased in order to extract the thermal units and the residue then becomes a valuable energy-saving by-product. In this context ash utilization can be viewed as an opportunity and not a problem. A step in the direction of full cycle reclamation was recently attained in the Midwest where a utility coal contract called for the supplier of the fuel to be responsible for the disposal of the resultant ash. It is expected much of this ash will end up back underground from whence it came.

Any discussion of ash utilization should naturally begin with the uses employed for the materials by utilities, themselves, and by the coal industry. Utilities all across the country are experiencing life-cycle cost savings in the construction of new generating facilities by utilizing their own materials. Then, too, ash sales tend to reduce the cost of coal burned by the utility-a significant factor in today's energy costs. Each ton of ash which is sold means a savings in disposal expense, and a 52 million ton mountain of ash represents a heap of dollars. Aside from the expected application of fly ash concrete, other significant applications around the stations include that of structural fill under the tall stacks and in other areas, for soil stabilization under floor pads supporting the generating units, base mixes for in-plant access roads and parking lots, sub-base material for rail sidings and coal storage yards, dikes around fuel storage areas, and in water impoundments.

Fires in abandoned coal mines have been successfully controlled with fly ash deployed by various grouting techniques. Now, a new procedure manual for extinguishing flames in an active operation is being developed by the U.S. Bureau of Mines based on a treatment program under way at Eastern Associated Coal Corporation's Joanne Mine at Rachel, West Virginia. The project calls for the sealing of the fire zone using fly ash injected with liquid nitrogen as the float agent and topped with a urethane foam. The work is being done in cooperation with Foster-Miller Associates, Inc.

Surface subsidence over worked-out mines has also been effectively minimized using fly ash to fill the voids left by underground mining. The ash is injected either in the dry state or in a water-cement grout through bore holes drilled into the problem areas. Auger holes have been sealed with a fly ash/cement mix.

Other coal operators have found fly ash to be a good media for controlling combustion on refuse piles. For example, Valley Camp Coal Company regularly adds 25 percent ash to all refuse going to its slag dump at its Shrewsbury Mine near Charleston, West Virginia, and reports it is 100 percent effective. Since the Buffalo Creek disaster there has been increased interest in utilizing ash to stabilize slurry impoundments. Additionally, many companies specify fly ash concrete for all construction around the mines and insist on the use of fly ash blocks for stoppings. The latter have only a fraction of the air leakage of conventional cement blocks and are less porous.

Increased pressure is being generated in many coal-producing states to find ways of revegetating the scars of abandoned surface mine spoil banks and coal refuse piles. Resource and conservation personnel are finding that fly ash can be utilized for this purpose. It is not a miracle material by any means nor a substitute for fertilizer or other plant nutrients. But the alkaline ash serves as a soil additive or conditioner to raise the pH of acid spoil to tolerable levels and to improve the water retention capability and thus help sustain plant growth. The techniques for applying the ash have been largely developed by specialists from the Morgantown Energy Research Center of the U.S. Bureau of Mines.

An experimental program is now under way with the Ohio Department of Natural Resources to determine the effectiveness of fly ash and sewage sludge in the treatment of orphan soil banks. Cement dust is being tried as a lime replacement on some plots. The project is a cooperative effort involving the Bureau of Mines, ODNR, Ohio Agricultural Research & Development Center, two utilities, a cement company, the NAA and two affiliated members.

Research conducted at the University of Notre Dame has demonstrated fly ash can be utilized in the treatment of various types of polluted waters and sewage. One field test showed ash improved the water quality in a polluted lake. Likewise, ash has the capability to neutralize synthetic and actual acid mine drainage waters in much the same manner as lime.

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A project now nearing completion at West Virginia University for the Environmental Protection Agency may open the door to the widespread use of fly ash in sanitary landfills. Tests have shown the ash accelerates the decomposition of household refuse and aids in the compaction of the refuse which would extend the expected life of such landfills. Injection grouting with fly ash is also being studied to stabilize a portion of an existing landfill operated by the City of Morganown near the WVU campus to determine the potential load bearing capabilities of the fill. Initial readings indicate the alkaline ash has a beneficial effect on the leachate emitted. Studies under way at Virginia Polytechnic Institute and State University indicate the ash can improve certain crop yields on poor or acidic soils. The Blacksburg agronomists are also observing soil conditioning results on pasture lands.

Our galloping inflation and growing shortages of natural aggregates and cement are resulting in increased uses of ash in the highway and construction fields. However, it would appear that modification of existing materials and construction specifications will be necessary before power plant aggregates (PPA) are fully accepted. In remarks before the Highway Research Board last year. Dr. Lyle K. Moulton of WVU Civil Engineering Department summed up the situation quite aptly when he stated: "In some instances better performance and greater economy were achieved with ash mixtures that did not meet existing specifications. If ash is to be used effectively in highway construction, new specifications must be developed that take into consideration the unusual properties of the ash and the specialized construction techniques required." Early in 1974, the U.S. Department of Transportation made Dr. Moulton somewhat of a prophet with two trail-blazing announcements. First, the Federal Aviation Administration announced approval of a new item in its Standard Specifications for Construction of Airports to permit the constructing of a base course by mixing, spreading, shaping, compacting mineral aggregates, lime, fly ash, and water. The Federal Highway Administration issued a memorandum to all field personnel and state highway officials urging acceptance of the use of fly ash in Portland cement concrete and in base course construction.

Since that time, highway departments in Minnesota, North Dakota, and in the District of Columbia have moved to amend specification requirements permitting the use of fly ash in portland cement pavement. Two other states, Virginia and West Virginia, are in the process of drafting new guidelines. And previously, both Florida and Georgia had adopted such standards.

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