"Innovations" Case Studies: New Uses for Old Tires

General Information

• Overview
• Tire Recycling Process

Overview

A key challenge facing local governments has been addressing waste tire disposal and recovery. Unlike most types of solid waste, waste tires cannot be simply landfilled without first being processed. This contributes to illegal dumping and the development of tire stockpiles. Discarded tires present a variety of hazards for the environment and public health, including providing habitat for disease-carrying vectors and creating the potential for fires at both illegal dumps and regulated tire stockpiles.

Within the last five years, the State of California has seen two of its largest tire stockpiles—located in Tracy and Westley—catch fire. These fires have raised concerns about the need to eliminate the existing stockpiles and to develop additional end uses for tires.

The state’s tire problem is significant. Californians produce more than 30 million discarded tires annually, representing 1 percent of the municipal waste stream by weight. Another three million tires are exported from nearby states. Seventy-two percent of the 34 million tires are being diverted to end uses such as reuse, retread, crumb rubber, and energy recovery. The state must find end uses for the remaining 8 million tires, which are currently being stockpiled, illegally dumped, or shredded and landfilled.

Efforts to reduce tire disposal and increase recovery have been driven by two diversion mandates. The first is the Integrated Waste Management Act (AB 939, Sher, Chapter 1095, Statutes of 1989 as amended [IWMA]). The second is the Tire Recycling Act (AB 1843, W. Brown, Chapter 974, Statutes of 1989). AB 1843 originally established a $0.25 per tire fee used to fund the tire programs of the California Integrated Waste Management Board (CIWMB).

AB 1843 was aimed at reducing the disposal and stockpiling of tires by 25 percent within four years and recycling and reclaiming used tires to the greatest extent possible. The law was amended by Chapter 838, Statutes of 2000 (SB 876, Escutia) which raised the fee to $1.00 per tire and expanded the responsibilities of the CIWMB.

State efforts to recover tires create an opportunity for local public works departments. New uses for old tires are providing creative ways to reduce waste, cut costs, and improve the quality and safety of public works projects.

Tires can become an important part of local public works projects in three key areas:

• Use of rubberized asphalt in local road projects.
• Use of tire shreds and rubber products in other civil engineering applications.
• Use of crumb rubber products in playground renovations.

This model study presents a detailed analysis of two tire recycling options for local governments: rubberized asphalt (Los Angeles County), and civil engineering fill (the State of Maine).

Tire Recycling Process

While this study is focused primarily on the development of innovative end use markets by local governments, they can play a role in each step of the tire recycling process.

Managing tires in the waste stream falls into three distinct phases: collection, processing, and end use. Local governments may be involved in one or more of these steps, but they are not usually involved in all three (that is, from collection through end use).

San Joaquin County has developed a comprehensive tire management program. The county established a tire amnesty program to collect old tires from the public. Staff contracted with a tire shredder to process the tires and then burned them at the local cogeneration facility in Stockton.

Collection

Collection presents the first challenge to dealing with tires. Collection is ongoing and is primarily the responsibility of tire dealers. Registered private haulers transport discarded tires to crumb rubber producers or other facilities for end use or disposal. Nevertheless, many tires may not get collected and are illegally dumped.

A local government may conduct an ongoing collection program, a one-time collection day event, an illegal pile cleanup, or a community cleanup program. An amnesty day program allows citizens to bring old tires (normally with a per-person tire limit) to a central drop-off location.

Processing

Depending on the end use, local governments will need to decide how to process the tires collected. For most tire management programs, this will entail working with a private company in the shredding or crumbing business. Shredding entails inspection for contamination (rocks, organics, bolts, and other metals), cleaning, debeading (pulling the steel bead from around the rim of the tire), and shredding.

The extent of the shredding process depends upon the desired shred size needed for a particular end use. The production of crumb rubber requires the extra step of granulating the small shreds to as small as 80 mesh size or as needed for the intended end use. In all cases, transportation of

whole tires to the processor or site will be a factor to consider. When the Davis Street Landfill in Alameda County closed and became a transfer station, the county’s waste management authority-along with the hauler-turned the site into a materials recovery park. One of the tenants is a tire shredder/processor.

The proximity to the urban service area has allowed many local governments to work closely with the processor both in cutting costs as well as in providing a supply of shreds and crumb for local use. The processor offers a “close the loop” discount for localities that supply tires for processing and purchase crumb rubber or shreds for end use.

End Uses/Markets

New uses for old tires are providing some creative ways to reduce waste, cut costs, and improve the quality and safety of public works projects. The potential uses for waste tires are endless. The cost-effectiveness and the state of development for end use markets vary considerably.

Three primary end use markets currently exist for waste tires: energy recovery, retreading, and crumb rubber products. Civil engineering fill is another major-but currently undeveloped-use for tires in California. In addition, there are a variety of other small end uses for tires.

Energy Recovery. In 2000, the largest single end use of tires in the state was energy recovery, consuming approximately 5.2 million tires in cement kilns, energy recovery facilities, or co-generation facilities. Several cogeneration facilities around the state are permitted to burn tires. These facilities are the most economical since they typically do not charge a tip fee to accept tires.

The Modesto Energy (MELP) facility, located adjacent to the Westley tire pile, was the only facility in the state to burn whole tires to produce electricity. The facility had been burning approximately 6 million tires per year, but it has been forced to close operations due to the recent tire pile fire and the inability to compete economically under energy deregulation. Several cement kilns around the state are currently permitted to burn tires as a supplement to their coal use. These facilities charge to handle tires.

In addition, two coal-fired cogeneration facilities are using tires as fuel supplements. About 10 percent of the heat input can be provided by waste tires. The Air Products facility in Stockton combusts more than 1 million shredded tires annually.

Retreading. In 2000, retreading consumed approximately 2.4 million tires. Retreading tires can be one of the most cost-effective methods of diversion; however, only certain tires can be retreaded due to their initial construction or excessive wear. Truck or heavy equipment tires are best suited for this. The cost savings over virgin tires make the operation profitable for both the retreader and the consumer. Cost savings to the consumer can exceed one hundred dollars per tire. This is a particularly attractive option for fleet users.

Crumb Rubber Products. Approximately seven million tires were used in crumb rubber production in 2000, primarily for both paving and molded products. Crumb rubber uses include; paving materials, rail crossings, sound barriers, industrial flooring, sealant, shoe soles, carpet pads, playground mats, pond liners, conveyor belts, recycling bins, oil spill absorber, floating docks, wharf pilings and buffers, agricultural pipes, animal bedding, and fencing.

• Paving Applications--A variety of State and local government agencies, including Los Angeles County and the California Department of Transportation (Caltrans), have proven that rubberized asphalt concrete is a significant and viable end use for tires.
• Molded Rubber Products--At present this market is still in its initial development stage but it represents the greatest potential for value-added recycling. The CIWMB has issued grants to various private businesses and public agencies for pilot projects to fund the development and purchase of molded rubber products.
• Soil Amendment--Tests and demonstration projects have shown crumb rubber used as an additive to soil can increase soil permeability as well as oxygen flow.

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Last updated: October 26, 2007