Assessment of Present Situation

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INTRODUCTION

About 242 million automotive, truck, and off-road tires are discarded in the United States each year. This is approximately equal to one waste tire per person per year. Additionally, there are 33.5 million tires that are retreaded and an estimated 10 million that are reused each year as second-hand tires. It is estimated that 7 percent of the discarded tires are currently being recycled into new products and 11 percent are converted to energy. Nearly 78 percent are being landfilled, stockpiled, or illegally dumped, with the remainder being exported.

Tires are difficult to landfill. Whole tires do not compact well, and they tend to work their way up through the soil to the top. As a result, tire stockpiles, which cost less thsm landfills, have sprung up all over the country. It is estimated that between 2 and 3 billion tires are stockpiled in the U.S. at present, with at least one pile containing over 30 million tires. Tire stockpiles are unsightly and are a threat to public health and safety. Not only are tire piles excellent breeding grounds for mosquitoes, but they are also fire hazards.

It is the goal of the EPA to eliminate illegal dumping altogether and to reduce the stockpiling and landfilling of discarded tires as much as possible. The report, The Solid Waste Dilemma: An Agenda for Action, lays out EPA's national strategy for managing municipal solid waste (MSW) (1). It sets out a three-tier hierarchy for management of municipal solid waste, with source reduction ranking first, followed by recycling, then incineration and land disposal. Interestingly enough, over the last 40 years, tires have been somewhat of a success story for source reduction. The advent of the 40,000-mile tire means that tires last longer before they wear out.

As with many other components of the waste stream, the highest priority options, source reduction and recycling, are the least utilized and landfilling is the most common practice. Potential source reduction measures for tires include the design of longer lived tires, reuse of tires removed from vehicles, and retreading. These practices all extend the useful life of tires before they are discarded. Considerable increases in tire lifetimes have been achieved in the past 20 years with the advent of the radial tire. On the other hand, partially because of the radial tires, retreading of automobile tires is decreasing each year. Radial tire side walls tend to be weaker than bias ply walls, thus the rejection rate by retreaders is higher. Radials also are more expensive to retread than bias plies. Truck tire retreading, however, is still increasing. A total of about 37 million tires were retreaded in 1987. This dropped to 33.5 million in 1990. Retreading extends the useful life of a retreadable tire from 60 to 80 percent (an automobile tire with one retread) to 300 percent (a truck tire with three retreads).

Tire recycling activities include the use of whole tires or processed tires for useful purposes. Whole tire applications include reefs and breakwaters, playground equipment, erosion control, and highway crash barriers. Processed tire products include mats and other rubber products, rubberized asphalt, playground gravel substitute, and bulking agent for sludge composting.

Scrap tire combustion is practiced in power plants, tire manufacturing plants, cement kilns, pulp and paper plants, and small package steam plants.

GENERATION OF WASTE TIRES

It is commonly accepted in the tire industry that about one tire per person per year is discarded. Since there is no industry group or governmental agency that monitors tire disposal in the United States, the best estimates that can be made are based on tire production. The Rubber Manufacturers Association (RMA) records the number of original equipment, replacement, and export tires that are shipped each year in the United States. (See Table 3.) In 1990, a total of 264,262,000 tires were shipped. The RMA data include new tire imports, but not imported used tires. To estimate the number of tires that were discarded in the United States in 1990, the following assumptions were made:

One tire is discarded for each replacement tire shipped, including new and used imports. (Discard is assumed to be in the same year as replacement tire production.)

Original equipment tires are not discarded in the year they are produced, but rather in the year a replacement is sold.

Exported tires are not discarded in the USA.

Four tires are discarded for each automobile or truck when it is taken out of service.

Retreads and reused tires are put back into service in the same calendar year that they were taken out. (Therefore, retreading and reuse simply have the effect of extending the tire's useful life.)

Table 3

U.S. AUTO, TRUCK, AND FARM TIRE SHIPMENTS* (In thousands of tires)

Original equipment Replacement Export Totals

1989

Passenger Bus/Truck

47,199 6,993

152,251 36,588

14,110 3,283

213,560 46,864

Farm

Equipment Total

995 55,187

2,549 191,388

294 17,687

3,838 264,262

Original equipment Replacement Export Totals

1988

51,170 8,177

151.156 35,172

12,437 3,548

214,763 46,897

890 60,237

2,664 188,992

270 16,255

3,824 265,484

Original equipment Replacement Export Totals

1987

54,131 8,801

155,294 33,918

9,365 3,301

218,790 46,020

753 63,685

2,662 191,874

267 12,933

3,682 268,492

Original equipment Replacement Export Totals

1986

52,913 7,845

151,892 34,514

5,987 2,069

210,792 44,428

608 61,366

2,658 189,064

226 8,282

3,492 258,712

Original equipment

Replacement

Export

Totals

54,392 6,859

144,267 32,392

4,032 1,302

202,691 40,553

512 61,763

2,319 178,978

170 5,504

3,001 246,245

* Includes imported new original equipment and replacement tires.

Source: Rubber Manufacturers Association (RMA) Monthly Tire Report, December 1990 and earlier years.

Although these are simplifying assumptions, they lead to a good approximation of the number of tires available for discard each year. Inaccuracies may result because sometimes when vehicles are de-licensed, they may remain in the junk yard or in a garage for a while before their tires are discarded. Also, when a tire is removed from a vehicle for retreading or reuse, a new replacement tire may take its place. For this replacement tire, there will be no corresponding discard. However, when the retreaded tire is sold again, a waste tire would be generated.

Table 4 summarizes waste tire generation based on the assumptions above. These data show that in 1990 scrap tires were generated at the rate of about 0.97 tires per person per year. Figure 2 and Table 5 show the estimated disposition of the 242 million scrap tires generated in 1990. About 16.3 million were recycled, 26 million were recovered for energy, and about 12 million were exported, leaving 188 million for landfilling, stockpiling, or illegal dumping. Figure 3 shows that in 1990 17.4 percent of the tires scrapped were recycled or burned for energy.

ENVIRONMENTAL PROBLEMS ASSOCIATED WITH WASTE TIRE STOCKPILES

Because of the difficulty of landfilling scrap tires and the resulting high costs, stockpiles have sprung up across the country. It is estimated that between 2 and 3 billion tires are stockpiled in the U.S. at present, with at least one pile containing over 30 million tires. In addition to being unsightly, tire piles are excellent breeding grounds for mosquitoes and they are fire hazards.

Mosquitoes

Mosquitoes have long been identified as pests and vectors of disease. It has also been known for some time that tires have the potential to serve as ideal breeding grounds for mosquitoes, especially when tires occur in large numbers in stockpiles. Because of the shape and impermeability of tires, they may hold water for long periods of time providing sites for mosquito larvae development.

Because tires can hold water, they have contributed to the introduction of non-native mosquito species when used tires are imported to the U.S. The new species are often more difficult to control and spread more disease (2).

There is evidence of tires contributing to the presence of mosquito-transmitted diseases. The main solution that has been offered is tire shredding. This guarantees that no water will be held for breeding sites. Further preventive measures could include requiring all shipped tires and all stockpiles to be fumigated. Other solutions sometimes suggested to the mosquito problem in tire stockpiles

SCRAP TIRE GENERATION IN THE UNITED STATES

(In Thousands)

Year

1984

1985

1986

1987

1988

1989

1990

Replacement Tire Shipments

Passenger 1/

144,580

141,455

144,267

151,892

155,294

151,156

152,251

Truck 1/

31,707

32,098

32,392

34,514

33,918

35,172

36,588

Farm Equipment 1/

2,592

2,395

2,319

2,658

2,662

2,664

2,549

Imported Used Tires 21

1,793

3,233

2,552

2,925

1,352

1,466

1,108

Total Replacement Tires

180,672

179,181

181,530

191,989

193,226

190,458

192.496

Tires from Scrapped Vehicles 3/

Cars

26,700

30,916

33,768

32,412

35.016

37,200 4/

39,000 4/

Trucks

6,408

8,400

9,236

9,456

9,004

10.400 4/

11,000 4/

Total Tires from Scrapped Vehicles

33,108

39,316

43,004

41,868

44,020

47,600

50,000

Total Scrap Tires in U.S.

213,780

218,497

224,534

233,857

237,246

238,058

242,496

U.S. Population (thousands) 3/

235,961

238,207

240,523

242,825

245,807

247.732

249,981

Scrap Tires/Person/Year

0.91

0.92

0.93

0.96

0.97

0.96

0.97

1/ (Includes imported new tires) National Petroleum News, Fact Book, 1986-1988. Data from the Rubber Manufacturers Association. 1988 through 1990 data from RMA Industry Monthly Tire Report, December 1989 and December 1990. 2/ U.S. Department of Commerce. *U.S. Imports for Consumption." (FT246). 1984-1990. 3/ U.S. Department of Commerce, Statistical Abstracts, 1990 and prior years. Estimate based on 4 tires per vehicle. 4/ Estimated by Franklin Associates, by linear extrapolation.

Figure 2. 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 5

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