In conclusion, the recycling of obsolete plastics is currently inhibited largely by technological factors and only marginally by economic parameters. Of those economic parameters, transportation appears to be one of the minor ones. The effects of railroad freight rates in this area of resource recovery are minimal at

most.

Fly ash and other industrial ashes.-Fly ash is a waste byproduct of the burning of coal at electric utility plants. The characteristic that distinguishes fly ash from other forms of coal ashes is its fineness. It consists of smooth, glassy particles, a single particle being so fine that it is invisible to the human eye. Chemically it consists principally of silica, iron oxide, alumina, and lime.

Fly ash generated in the United States amounted to 27.1 million tons in 1971, a 2.3-percent increase over the 1970 production. (See the table below entitled Production and Utilization of Ash in the U.S.) Of the total fly ash generated in 1971, 11.8 percent was utilized, in comparison with a 8.3-percent utilization rate in 1970. From 1965 through 1970, the average annual utilization rate was 11.2 percent. (See the table below entitled Ash Collection and Utilization Survey Year 1969.)

Production and Utilization of Ash in the U.S., 1966-1971

*Fly ash, boiler slag, and bottom ash.

Source: Edison Electric Institute, Fuel and Ash Subcommittee--Published by National Ash

Association.

346 I.C.C.

132,226

5,000

170,450

5,686

176,788

73,240

Lightweight aggregate------

964,578

Electric utility companies need to dispose of mountains of ash residue that accumulate at coal burning power stations. As with most waste, the alternatives for disposing of this accumulation of ash are becoming more and more restricted. Many utility companies, especially those with plants in urban areas, must have ash hauled great distances, sometimes 70 miles or more, to be dumped. Disposal costs vary from $0.20 to as much as $2.50 per ton, with an average disposal cost of $0.50 per ton (which is estimated as increasing to $1 by 1975).136 The Potomac Electric Power Company, serving Maryland, Virginia, and the District of Columbia, pays $2 per ton for disposal of its ash by truck. In rural areas, where there is more space for dumping, disposal costs, of course, are considerably lower.

According to industry sources, a major problem in fly ash disposal is educating potential users about its suitability for replacing heavyweight aggregate, the supply of which is declining rapidly in some parts of the country, and the numerous other applications for which ash is a low cost, plentiful, and locally available resource. '37 Despite the potential of fly ash for other purposes, it is now used primarily as an additive. Before it can be marketed, the ash must be tested for its suitability as an admixture. It is important that the ash meet certain chemical and physical requirements. The American Society of Testing Materials, Department of Interior's Bureau of Reclamation, and the U.S. Army Corps of Engineers have developed specifications for the use of fly ash in concrete and other products. As a recycled material, fly ash currently has the following applications:

1. an additive to cement in concrete and as a raw material or a portion of the kiln feed in the production of cement for dams, masonry block, pipe, and precast units, 2. a mineral filler in bituminous or asphaltic concrete for road surfacing,

3. a raw material in the production of pozzolanic pavement as a stabilizing base for runway and other construction,

4. as a material for the production of lightweight aggregate for processing into lightweight concrete and concrete products,

5. as structural fill for road and other construction (the largest single use), and 6. an abrasive: as oil well grout; a control agent for mine fires and subsidence (sinking) of terrain over abandoned mines; a precipitate in sewage treatment; and a filler or aggregate in asphalt shingles, foundry sand, and chemical products.

Many States permit the use of fly ash in asphalt mixes used for road construction or maintenance. However, present consumption 136Estimate of the National Ash Association.

137 A Look at the Flyash Picture," a speech by Mr. John Faber, Executive Vice President, National Ash Association, Inc., Washington, D.C.

of this material as an additive is relatively insignificant when compared with its potential. It has been estimated that if fly ash were used as a mineral filler for the eventual resurfacing of all existing bituminuous surfaced roads, almost 300 million tons of ash would be required-about 12 times the current U.S. fly ash annual output.

It is anticipated that the use of fly ash in lightweight aggregate production will increase considerably in the future. The process by which the ash is converted to aggregate, called "sintering," can be performed close to the source of the ash, the aggregate can be stored in open piles, and most of the production probably can be consumed locally. Thus, storage and transportation problems will be minimized, keeping the product costs low and enhancing its advantage over rapidly dewindling natural aggregate sources.

Average Price* per Ton, Fly Ash and Substitute-1969

**Crude volcanic ash sells at $1.11 per ton. Price range for usable ash in 1968 was from $0.90 to $4.23 depending on form and quality.

***Utility companies sell fly ash at $1.25 per ton. Grading, testing, and storage require additional charges.

Sources: U. S. Department of Labor, Wholesale Prices and Price Index (1969); Bureau of Mines, Mineral Facts and Problems (1970) and Minerals Yearbook (1970); and Walter Handy Company (marketers of fly ash).

Another potentially large use of ash is in the manufacture of bricks, at qualities and prices competitive with clay brick. Researchers at the University of West Virginia have made considerable progress on the use of fly ash and bottom ash in the production of brick. The fly ash brick is composed entirely of the byproduct of pulverized coal furnaces and passes all American Society of Testing Materials requirements for high quality face brick. Cost studies indicate the product may be manufactured at a cost below that of clay brick and marketed at a price to compare with the highest quality clay material. The Nation's need for residential and commercial construction materials can be expected to create a sizable demand for fly ash brick.