Piling It On

SCRAP TIRE PILES may be a pet peeve of solid waste managers, but three reuse markets are available to help alleviate the eyesores and potential health hazards that old tires create.

Tire-derived fuel (TDF), civil engineering applications and ground rubber are growing applications for scrap tires. In fact, approximately 218 million tires or 77 percent of the total number of tires generated in 2001 were sent to an end-use, according to the Rubber Manufacturers Association (RMA), Washington, D.C. In comparison, only 11 percent of the 240 million scrap tires generated in 1990 were reused.

TDF is the oldest and largest use for scrap tires, despite various challenges. Such challenges have included opposition from environmentalists and public opposition who fear emissions or black smoke. Also, it's difficult to obtain permits for TDF facilities.

However, according to the RMA's 2001 Scrap Tire Market Study, in 2001, 115 million tires were consumed as fuel. Cement kilns, pulp and paper mill boilers, and industrial and utility boilers all can use TDF to supplement other fuel sources. And as industries gain a better understanding of TDF and its ability to reduce emissions, TDF has a strong outlook. Additionally, TDF may become even more attractive as energy prices increase.

While TDF may be the SCRAP tire reuse industry heavyweight, civil engineering applications of mostly shredded tires represent the fastest growing end-use market. Civil engineering applications involving landfill construction have helped to use 35 million of the 40 million tires used in this area in 2001, according to RMA. Particularly, using shredded tires as construction material in landfills has become more popular. Shredded scrap tires can be used in leachate liners, gas-venting systems, cap closure material, operational liners and as a daily cover when mixed with dirt.

Ten years ago, less than 1 million scrap tires were used in civil engineering applications and few, if any, technical reports existed to evaluate their effectiveness. Artificial reefs, dock bumpers and breakwaters constituted the majority of uses. However, scrap tire processors now view the civil engineering market as a way to move large-scale amounts of otherwise unusable or unmarketable products into a cost-recovery situation. Tire shreds are said to be cost-competitive with other construction materials such as dirt, rock and clean fill. A listing of ASTM International standards for the “Use of Scrap Tires in Construction Applications” currently are available from ATSM, Conshohocken, Pa., or the RMA.

Another end-use market that has increased recently is the use of “coarse” rubber particles (½ inch to 4 mesh in size), primarily for playgrounds, soil amendment or formed into blocks for flooring. Also, ground rubber (or crumb rubber) markets have surged during the last two years, with playground surfaces, soil amendments and asphalt heavily contributing to its growth.

At one time, the U.S. Environmental Protection Agency (EPA), Washington, D.C., had estimated that there were approximately 2 billion to 3 billion scrap tire stockpiles across the country. In 1994, the RMA contacted all 50 states and found that there were approximately 880 million tires stockpiled. But from 1991 to 2001, the majority of states aggressively abated their stockpiles. The RMA's study found that the number of stockpiled tires have been further reduced to 306 million.

The majority of states have less than 1 million tires in stockpiles. Stockpiled tires primarily are found in Texas, New York, Ohio, Michigan, Alabama, Pennsylvania, Virginia and Massachusetts. This includes stockpiled tires, not tires that are legally landfilled. Unfortunately, only half of the states with tire piles have active stockpile abatement programs or anticipate creating programs.

Once tires are removed from stockpiles, a processor's return on investment usually is not a major issue because abatement programs typically entail state-funded tire removal. However, stockpiled tires normally can only be used for TDF and in civil engineering applications because dirt is not a concern in those end-markets. In civil engineering applications, tire shreds often are covered with a dirt fill anyway.

While scrap tires reuse markets have expansion potential, the markets are unevenly distributed across the country. Some states and regions (Mid-Atlantic states through the Southeastern), have strong scrap tire infrastructures where supply and demand almost are equal. Other states, however, have few end-use markets and little likelihood of future market development. So to achieve total success in scrap tire management, more effort still is needed.