Executive Summary

The management of scrap tires has become a growing problem in recent years. Scrap tires represent one of several special wastes that are difficult for municipalities to handle. Whole tires are difficult to landfill because they tend to float to the surface. Stockpiles of scrap tires are located in many communities, resulting in public health, environmental, and aesthetic problems.

This report discusses the problems associated with scrap tires and identifies existing and potential source reduction and utilization methods that may be effective in solving the tire problem. Barriers to increased utilization and options for removing the barriers are identified and evaluated.

The Scrap Tire Problem

Over 242 million scrap tires are generated each year in the United States. In addition, about 2 billion waste tires have accumulated in stockpiles or uncontrolled tire dumps across the country. Millions more are scattered in ravines, deserts, woods, and empty lots. Scrap tires provide breeding sites for mosquitoes which can spread diseases and large tire piles often constitute fire hazards. Most tire and solid waste professionals agree that a tire problem exists.

Six facets of the tire problem are listed below:

Tires are breeding grounds for mosquitoes. Besides the major nuisance of mosquito bites, mosquitoes can spread several serious diseases.

Uncontrolled tire dumps are unsightly and are fire hazards. Fires in tire dumps have burned for months, creating acrid smoke and leaving behind a hazardous oily residue. A few tire fire locations have become Superfund sites.

Tires should be utilized to minimize environmental impact and maximize conservation of natural resources. This means reuse or retreading first, followed by reuse of the rubber to make rubber products or paving, and then combustion and disposal. At present, the preferred uses do not accommodate all the tires, and disposal must be utilized to a large degree.

Waste tires have to go somewhere. They tend to migrate to the least expensive use or disposal option. As costs or difficulties of legal disposal increase, illegal dumping may increase.

Disposing of waste tires is becoming more expensive. Over the past 20 years the average tipping fees for disposing of tires have continually increased. This trend is likely to continue as landfill space becomes more scarce.

Tires take up landfill space. Whole tires are banned from many landfills or charged a higher tipping fee than other waste; even if they are carefully buried to prevent rising they are very bulky. Shredded tires take up less space, but it is space that could be saved if the tires were utilized as raw material for products or as fuel.

As described above, the continuing accumulation of waste tires has led to six concerns of varying severity. Clearly, the mosquito and fire hazard problems are the most serious of the concerns listed. Controlling them in the near term will necessitate providing adequate safeguards on existing stockpiles. Ultimately, decreasing the waste tire accumulations will involve appropriate uses of recycling, combustion, and landfilling. The current trends of reuse and source reduction indicate that the quantity of tires utilized in products is likely to remain smaller than the quantity combusted or landfilled in the future.

It is estimated that less than 7 percent of the 242 million tires discarded in 1990 were recycled into new products and about 11 percent were converted into energy. Over 77 percent, or about 188 million tires per year, were landfilled, stockpiled, or illegally dumped, and the remaining 5 percent were exported. The flow of scrap tires is shown in Figure 1.

Scrap tire legislation is increasing rapidly at the state level. In 1990, twelve states passed or finalized scrap tire laws, regulations, or amendments. As of January 1991, thirty-six now have scrap tire laws or regulations in effect, and all but 9 states regulate or have bills being proposed to regulate tires. A summary of the states' laws in effect in January 1991 are listed in Table 1. The contents of the legislations and the sources of funding are summarized in Table 2.

Figure 1. Flow diagram showing estimated destination of scrap tires in 1990. (In millions of tires and percent)

* Retreads (33.5 million) and reused tires (10 million) are not counted as scrap tires.

Tabla 1

SCRAP TIRE LEGISLATION STATUS January, 1991

Draft Proposed Regs Law

Tabla 1

SCRAP TIRE LEGISLATION STATUS January, 1991

Draft Proposed Regs Law

Alabama

X

Montana

Alaska

Nebraska

Arizona

X

Nevada

Arkansas

X

New Hampshire

California

X

New Jersey

Colorado

X

New Mexico

Connecticut

X

New York

Delaware

North Carolina

Florida

X

North Dakota

Georgia

Ohio

Hawaii

Oklahoma

Idaho

Oregon

Illinois

X

Pennsylvania

Indiana

X

Rhode Island

Iowa

X

South Carolina

Kansas

X

South Dakota

Kentucky

X

Tennessee

Louisiana

X

Texas

Maine

X

Utah

Maryland

X

Vermont

Massachusetts

X

X

Virginia

Michigan

X

Washington

Minnesota

X

Wisconsin

Mississippi

X

West Virginia

Missouri

X

Wyoming

Drall Proposed Regs Law

Draft - draft being written/bill in discussion Prop - proposed/introduced in 1990 legislature

Regs - regulated under specific provision of solid waste or other laws (e.g., Law - scrap tire law passed

automotive wastes)

Source: Scrap Tire News, Vol. 5, No. 1, January 1991

Table 2

CONTENTS OF SCRAP TIRE LEGISLATION

Funding Source

Arizona

California

Colorado

Connecticut

Florida

Illinois

Indiana

Iowa

Kansas

Kentucky

Louisiana

Maine

Maryland

Michigan

Minnesota

Missouri

Nebraska

New Hampshire

North Carolina

Ohio

Oklahoma

Oregon

Pennsylvania

Rhode Island

South Dakota

Tennessee

Texas

Utah

Vermont

Virginia

Washington

Wisconsin

2% sales tax on retail sale $0.25/lire disposal tee

$1.00/tire retail sales $0 .SO/vehicle title lee permit fees/lire storage sites

$0.50/tire retail sales $t.00/lire retail sales ft.OO/tire disposal tea state budget appropriations $0.50 vehicle title tee $4.00/vehide title transfer *0.50/tire retail sales tt.OO/tire retail sales graduated vehicle regis! lee 1% sales tax on new tires

$100/new Dre (surcharge) 4t.00/new tire (dspl tax)

$0 50/new tire sales tax graduated tax per tire size }0 50/new tire (dspl tax) $2.00Aire vehicle title lee

Storege

Processor Regs

Hauler

Landfill Restrictions*

Merkel Incentives draft X X X X

R&D grants grants'loans grants grants grants/loans grants grants funds/testing grants lunds/collection grants $0.01/lb R&D giants

$20/lon lunds/testing grants $20/lon to

s er

The majority of slates have imposed regulations that require tires to be processed (cut. sliced, shreeded) prior to tandfilling Some of the states allow for storage (above ground) of shreds at landfills. OH, NC, CO are among the suites considering or allowing monoftls for tire shreds. Whole tires are discoraged from landfills (in almost all cases) either by law (e.g., MN) or more frequently by high disposal fees.

Source: Scrap Tire News, Vol. 5, No. 1, January 1991.

Source Reduction Alternatives

Source reduction measures for tires include the following:

• Design of extended life tires

• Retreading

Great strides have been made in the last 40 years in tire manufacturing that have more than doubled the useful life of tires. Forty thousand mile tires are commonplace, and 60,000 to 80,000 mile lifetimes are often achieved. Constraints of cost, fuel consumption, and comfortable rides, make it unlikely that any major design changes will occur in the near future that will significantly increase tire life.

Frequently, when one or two tires of a set are worn, the entire set is replaced with new tires. Useful tread may remain on several of the remaining tires. These tires are often sold for second cars or farm equipment. About 10 million tires per year are currently being reused. Although the reuse of partially-worn tires cannot be expected to solve the tire problem, reuse could potentially double based on the number of good tires currently thrown away.

Retreading is the application of a new tread to a worn tire that still has a good casing. There are currently over 1,900 retreaders in the United States and Canada; however, that number is shrinking because of the decreased markets for passenger retreads. This decline is primarily due to the low price of new tires and the common misperception that retreads are unsafe. The price of inexpensive new passenger tires ($50 to $60) is often at or near the price of quality retreads. On the other hand, truck tire retreading is increasing. Truck tires are often retreaded three times before being discarded and the truck tire retreading business is increasing.

The National Tire Dealers and Retreaders Association asserts that properly-inspected retreaded tires have lifetimes and failure rates comparable to new tires. Mileage guarantees and/or warranties for retreads are often similar to or identical to new tire warranties. In 1987, about 23 million passenger and light truck tires and 14 million truck tires were retreaded. By 1990 these retread rates changed to 18.6 million and 14.9 million, respectively. It is estimated that most good truck tire casings are being retreaded due to the high cost of new truck tires, but that at least two times as many passenger and light truck tires would be suitable for retreading.

Recycling Alternatives

Some recycling alternatives use whole tires, thus requiring no extensive processing; other alternatives require that tires be split or punched to make products; and still other alternatives involve tires that are finely ground enabling the manufacture of crumb rubber products. Some applications for each alternative are listed below:

- Whole tire applications

• Artificial reefs and breakwaters

• Playground equipment

• Erosion control

• Highway crash barriers

- Split or punched tire applications

• Floor mats, belts, gaskets, shoe soles, dock bumpers, seals, muffler hangers, shims, washers, and insulators

- Shredded tire applications

• Lightweight road construction material

• Playground gravel substitutes

• Sludge composting

- Ground rubber applications

• Rubber and plastic products; for example, molded floor mats, mud guards, carpet padding, and plastic adhesives

• Rubber railroad crossings

• Additives for asphalt pavements

All of the tire recycling alternatives listed above are being used to varying degrees. However, the total usage of tires for recycling currently is estimated to be less than 7 percent of the annual generation. The markets for most of the products may be increased, but, even if increased to their fullest potential, appear to be small compared to the number of tires generated each year. Ground rubber applications hold the greatest promise. The tire recycling alternative with the greatest potential to significantly reduce the scrap tire problem of the United States is in asphalt highway construction.

There are two types of processes for using crumb rubber in pavements. One application, referred to as rubber modified asphalt concrete (RUMAC), involves replacing some of the aggregate in the asphalt mixture with ground tires. The second, called asphalt-rubber, blends/reactivates a certain percentage of the asphalt cement with ground rubber. Both systems are being evaluated by state agencies as well as the federal government.

Tire to Energy Alternatives

Tires have a fuel value of 12,000 to 16,000 Btu per pound, slightly higher than that of coal. With existing technology, tire combustion can meet Federal and State environmental requirements. Tires may be burned whole or shredded into tire derived fuel (tdf). Whole tire combustion requires less processing expense; however, most of the plants currently burning tires for fuel do not have the capability to burn whole tires. In 1990, about 25.9 million tires (10.7 percent of total generation) were burned for energy production. Combustion facilities currently using tires as fuel include:

• Tire manufacturing plants

• Pulp and paper plants

• Small package steam generators

The largest scrap tires combustion system is the Oxford Energy plant in Modesto, California. It consumes about 4.9 million tires per year and generates 14 MW of power. A second Oxford Energy power plant, designed to burn about 9-10 million tires per year, is under construction in Connecticut. Commercial operation is planned for 1991.

Seven cement kilns in the United States utilize about 6 million scrap tires per year to replace conventional fuels. Cement kilns appear to be ideal for scrap tires because of their high operating temperatures (2,600 F) and good conditions for complete combustion, which minimize air pollution problems. Also, there is no residue, since the ash is incorporated into the cement product. Of the 240 cement kilns in the United States, about 50 are equipped with precalciner/preheaters, making them most suitable for tire combustion.

Many furnaces designed to burn wood chips at pulp and paper plants are suitable for burning tire-derived-fuel without major modifications. Frequently, only wire-free tdf can be used in these boilers, thus increasing the tire processing costs. An estimated 12 million tires per year are currently being consumed by the pulp and paper industry.

Pyrolysis Alternatives

Pyrolysis of tires involves the application of heat to produce chemical changes and derive various products such as carbon black. Although several experimental pyrolysis units have been tried, none has yet demonstrated sustained commercial operation.

Barriers to Increased Scrap Tire Utilization

Barriers to increased scrap tire utilization can be classified into two main types - economic and noneconomic.

Economic barriers refer to the high costs or limited revenues associated with various waste tire utilization methods which make the uses unprofitable. Tire processors will not invest time or capital unless there is a sufficient rate of return to justify the efforts.

Noneconomic barriers refer to a number of constraints on utilization. These include technical concerns such as lack of technical information or concerns regarding the quality of products or processes. These barriers also include the reluctance of consumers, processors, and regulators to employ new approaches or technologies for aesthetic or other reasons. They also include constraints on utilization because of health and safety, environmental issues, laws, and regulations.

The strength and persistence of these barriers are evident from the continuing buildup of tire stockpiles and dumps over the last several years.

Most of the technologies available for mitigating the nation's scrap tire problem are limited by both economic and noneconomic barriers, and it is often difficult to separate the two. For example, the use of retreaded or used automobile tires is limited by competitive new tire prices, an economic barrier, as well as consumer concerns about safety and reliability, a noneconomic barrier. Designing tires to last 100,000 miles or more would cost considerably more and also would likely result in rougher rides and more tire noise.

Making products such as reefs, playground equipment, floor mats, gaskets, etc., out of scrap whole or processed scrap tires is primarily limited by the high cost of tires compared with other raw materials. However, there are also some noneconomic barriers. Reefs made of tires, for example, are not appropriate for the rough shores of the northwest. Playground equipment made of wood or other products is often preferred for aesthetic reasons.

The two technologies with the most potential for using a major portion of scrap tires generated each year, and actually reducing the tire stockpiles, are pavements with rubber additives and combustion for energy generation.

Barriers to the increased usage of rubber in asphalt pavements are both economic and noneconomic in nature. The cost of installing roads of rubberized asphalt is greater than conventional asphalt, which is an economic barrier. On the other hand, several studies show that the total life cycle cost of rubberized asphalt is lower than conventional asphalt. This would be an economic benefit. However, decisions on paving are often made on the basis of road miles paved per year, rather than life cycle cost of the pavement.

The two forms of rubberized asphalt that have been tested the longest, asphalt-rubber and PlusRide™, are patented. The required royalty fees increase the cost of these products. Although, initially, patents may have stimulated the growth of these products, they now appear to represent an economic barrier to increased scrap tire usage by these technologies. The patent for asphalt-rubber expires in 1991. After that more companies are expected to become involved, resulting in lower costs. Non-patented rubberized asphalt roadways are also being tested.

One of the major noneconomic barriers to the use of rubber in asphalt pavements has been the lack of consensus on the results of long-term testing. Many long-term tests have been performed, but they were performed in over a dozen states, and as yet these tests have not been brought together and evaluated in a cohesive study.

Power plants to burn scrap tires involve large capital investments and annual operating expenses. However, plants located near large supplies of tires can be feasible. A key variable in determining economic feasibility for these plants is the buy-back rate granted by the utility. In areas of the country where the rate is high, such as California and the northeast, power plants are feasible. The buy-back rate is the rate the utilities pay for electricity generated from alternative fuel, and reflects the fuel and other costs avoided by the utility.

Burning tires in existing pulp and paper mills and certain types of cement kilns requires much less capital investment than the dedicated power plants mentioned above. Pulp and paper mills often burn hog-fuel (chipped wood), thus requiring very little modification for tire chips. The main economic variable is the price of the competing fuel. Tire-derived fuel must often compete with low cost coal or petroleum coke, a waste product from the petroleum refining process. If tdf is only slightly cheaper than the alternate fuel, then plant modification cannot be justified.

The main noneconomic barriers to scrap tire combustion are the time required for permitting a plant and the concerns of neighbors regarding environmental, health, and safety issues. Because of the test burns required and time delays in permitting, many cement plant and pulp and paper mill operators hesitate to change their operation for the small savings realized by burning scrap tires.

Options for Mitigating the Scrap Tire Problem

There is now a general public awareness throughout the U.S. that a waste tire problem exists. A number of options have been identified to address the problem, many of which are currently being utilized in several states. State, local, and federal governments need to work on the waste tire problem from all possible angles, in order to arrive at a strong solution.

State governments have been very active in utilizing a variety of techniques for addressing tire problems. By the end of 1990, thirty-six states had regulated scrap tires, up from only one state in 1985. Twenty-one states had funded their state tire management programs through such means as a tax or surcharge on tires, added vehicle registration fees, or fees to transfer vehicle titles. Twenty-four states had final regulations addressing storage of tires. At least twelve states had included some type of market incentives such as rebates, grants or loans to help build markets for scrap tires.

These state laws can make a significant dent in solving the nation's tire problem. Particularly important provisions are funding sources based on taxes or fees on tires sold or on vehicles sold or transferred; mandates to clean up of tire dumps; regulations to reduce fire and mosquito hazards at tire stockpiles; and recordkeeping and tracking requirements to ensure that tires are sent only to reputable haulers, processors, or end-users who manage the tires legally. Market incentives such as the rebate systems instituted by the states of Oregon, Wisconsin, Utah, and Oklahoma, have been very successful in promoting additional recycling and the use of tires for energy recovery.

In addition to the state regulations, other ideas that have been implemented or proposed to address scrap tires, include: (1) procurement strategies; (2) research; (3) increased coordination among states; (4) education and promotion; (5) waste exchanges; (6) tradeable credits; and (7) tax incentives.

EPA's Federal procurement guidelines for retreaded tires, which became effective on November 17,1989, are encouraging Federal agencies both to retread tires on their vehicles, and to buy retreaded tires. States may decide to develop similar guidelines to encourage retreaded tires.

There is a need to continue to perform research on methods of recycling tires, such as the use of crumb rubber in rubber products and plastics. Existing research on rubberized asphalt should be summarized, and a decision made regarding its feasibility for more widespread use, or if there are still technical or economic questions, determining exactly what additional research is needed to answer these questions, and then perform this research. States and Federal government, and environmental and transportation agencies, should coordinate research efforts so that fewer, more comprehensive research projects (particularly related to rubberized asphalt) can be performed.

Other means of exchanging information such as conferences on scrap tires, hotlines, newletters, waste exchanges, and computerized data bases, are being developed or utilized by both government and industry. Because the economics and technology of scrap tires is changing so rapidly, these sources are particularly helpful in spreading information regarding scrap tires, to government officials, entrepreneurs, environmental groups, and private citizens.

Study Conclusions

Each year about 242 million tires are scrapped. Current trends indicate that less than 7 percent of these tires are being recycled as products and 11 percent are being burned for energy, and 5 percent are being exported. The rest are being landfilled, stockpiled, or dumped illegally.

EPA wishes to encourage waste tire reduction and recycling, with a special emphasis on reducing the number of tires in uncontrolled stockpiles or illegal dumps. These tires are often sites of mosquito infestation, with the potential for spreading dangerous mosquito-borne diseases. Large tire dumps can also lead to fires with major releases of hazardous organic chemicals into the air, surface water, and ground water.

Recycling rubber from tires for use in asphalt pavements is a promising technology. Asphalt pavements incorporating tire rubber are claimed to have twice the lifetime of ordinary asphalt, but they can cost twice as much. Pavements with crumb rubber additives consume over one million tires per year now, and both asphalt-rubber and rubber modified asphalt concrete have considerable potential for expansion. If Federal, state, and local governments promote much broader use and demonstration of this technology, perhaps the technical issues will be resolved and usage will expand.

Using whole tires as fuel for reciprocating grate power plants appears to be economically feasible in some regions of the country, and can meet environmental permitting requirements. One such plant in Modesto, California, is currently consuming 4.9 million tires per year. Another power plant is under construction in Connecticut and is expected to consume an additional 10 million tires per year. A second 10 million tire per year plant is being planned for an area near Las Vegas, Nevada. The main barriers to such plants appear to be local resistance to incineration projects and lengthy permitting procedures.

The replacement of coal by tire-derived-fuel appears economically feasible for cement kilns. Seven such kilns are currently operating in the U.S., consuming the equivalent of about 6 million tires per year between them. There is potential for this use to expand further, particularly for those cement kilns whose feed systems are compatible with the use of TDF.

Tire-derived fuel is economically feasible for use in hog fuel boilers in the pulp and paper industry. It is estimated that the equivalent of 12 million tires is consumed annually in this way in the U.S. There is potential for this use to expand further.

Other technologies and options are promising on a smaller scale, but also are important to the overall solution. Uses of crumb rubber for such diverse products as athletic surfaces, tracks, and rubber molded products, show potential for growth. Also, increased retreading could utilize a significant number of tires. If the market justified retreading all the usable carcasses, about 20 million additional passenger and light truck tires could be retreaded each year. Current trends, however, indicate that fewer of these tires are retreaded each year.

Other uses of tires are sometimes feasible for specialized geographic conditions. Cape May County, New Jersey uses 100,000 tires per year, which is 100 percent of its scrap tires, for artificial reefs. The State of Minnesota has used about a million of its tires since 1986 for roads in swampy areas.

The markets for most other products made from tires have potential, but appear to be relatively small. These include rubber railroad crossings, artificial reefs, playground equipment, erosion control, highway crash barriers, playground gravel substitute, sludge composting, rubber farm and agricultural equipment, and rubber mats. Each of these products has the potential for using some portion of our waste tire stockpile. Collectively, they are all important parts of the solution to the tire problem.

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