Tire Life Cycle

The tire life cycle can be identified by the following six steps: 1) Product developments and innovations such as improved compounds and camber tire shaping increase tire life, increments of replacement, consumer safety, and reduce tire waste. 2) Proper manufacturing and quality of delivery reduces waste at production. 3) Direct distribution through retailers, reduces inventory time and ensures that the life span and the safety of the products are explained to customers. 4) Consumers’ use and maintenance choices like tire rotation affect tire wear and safety of operation. 5) Manufacturers and retailers set policies on return, re-tread, and replacement to reduce the waste generated from tires and assume responsibility for taking the ire to its grave or to its reincarnation. 6) Recycling tires by developing strategies that combust or process waste into new products, creates viable businesses, and fulfilling public policies..

Landfill Disposal

Tires are not desired at landfills, due to their large volumes and 75% void space, which quickly consumes valuable space. Tires can trap methane gases, causing them to become buoyant, or ubble to the surface. This ubbling effect can damage landfill liners that have been installed to help keep landfill contaminants from polluting local surface and ground water. Shredded tires are now being used in landfills, replacing other construction materials, for a lightweight backfill in gas venting systems, leachate collection systems, and operational liners. Shredded tire material may also be used to cap, close, or daily cover landfill sites. Scrap tires as a backfill and cover material are also more cost-effective, since tires can be shredded on-site instead of hauling in other fill materials. In 2003, 38 states banned whole tires from landfills, 35 allowed shredded tires, 11 banned all tires from landfills, 17 allowed processed tires in mono-fills, and 8 states had no restrictions on scrap tires in landfills (Rubber Manufacturers Association, 2003).

Stockpiles and Illegal Dumping

Tire stockpiles create a great health and safety risk. Tire fires can occur easily, burning for months, creating substantial pollution in the air and ground, (in the U.S., becoming Superfund cleanup sites.) Recycling helps to reduce the number of tires in storage. The United States has decreased the number of waste tires in storage from 700-800 million in 1994, down to 275 million tires in 2004 primarily due to state scrap management programs (Rubber Manufacturers Association 2004). An additional health risk, tire piles provide harborage for vermin and a breeding ground for mosquitoes that may carry diseases. Illegal dumping of scrap tires pollutes ravines, woods, deserts, and empty lots; which has led many states to pass scrap tire regulations requiring proper management. Tire amnesty day events, in which community members can deposit a limited number of waste tires free of charge, can be funded by state scrap tire programs, helping decrease illegal dumping and improper storage of scrap tires.

Ultrasound recycling

High-power ultrasound is applied to the cured rubber during extrusion, and the high pressure, heat and mechanical energy break the cross-links, making the extrudate a gum rubber-like new material, that can be re-cured and molded into new rubber products.

Tire Pyrolysis

The pyrolysis method for recycling of used tires is an innovation technique that uses a special mechanism to heat the used tires in a closed, oxygen-free environment a stove to melt down the tires into the materials that they were made of. There are many different ways to achieve the melting procedure. For a long time, external heating methods were used. Recently an electroagnetic field technology was developed by Coral group, in Dnepropetrovsk, Ukraine. This method produces carbon, metal, gas and artificial oil as by-products of the recycling process. The quality of these by-products depends on the heating technique used, with simple outside heating techniques producing heavy oils (mazut); however, newer techniques that produce a ofter pyrolysis produce by-products such as benzene, kerosene and diesel.

Microwave recycling

The process of remediation of tire waste using microwaves to excite the rubber until it is in a gaseous state which will be condensed into its component parts including #3 diesel,syngas as well as carbon black and plated steel. No emissions are created in this process and all components can be reutilized.

Mechano-Chemical Recycling

There have been attempts to devulcanize waste tire material using chemical agents in combination with a milling process.

Markets

As of 2007, the EPA reported that of the 7.48 million tons of rubber materials that constituted solid waste, only 1.1 million tons of this was “reclaimed” (recycled). This is contrasted with a report from 2003, in which the EPA claims markets existed for 80.4% of scrap tires, about 233 million tires per year. Assuming 22.5 lbs per tire, the 2003 report predicts a total weight of about 2.62 million tons from tires.

The markets predicted by the 2003 report were: Tire Derived Fuel (TDF) using 130 million tires, Civil Engineering Projects using 56 million tires, Ground Rubber turned into molded rubber products using 18 million tires, Ground Rubber turned into rubber-modified asphalt using 12 million tires, Exported items using 9 million tires, Cut/Stamped/Punched Products using 6.5 million tires, and Agricultural and Misc. uses using 3 million tires.

Tire Recycling Supply Chain

The Tire Recycling Supply Chain is divided into three stages:

Tire-derived products stage

Second stage of tire recycling involves the production of alternate products for sale. New products derived from waste tires generate more economic activity than combustion or other low multiplier production, while reducing waste stream without generating excessive pollution and emissions from recycling operations..

Tire-derived products

Whole tires can be reused in many different ways. One way is for a Steel mill to use the tires as a carbon source, replacing coal or coke in steel manufacturing. Instead of mining coal from the ground and then burying tires in landfills, the tires are used directly. Tires are also bound together and used as different types of barriers such as: collision reduction, erosion control, rainwater runoff, wave action- that protects piers and marshes, and sound barriers between roadways and residences. Entire homes can be built with whole tires by ramming them full of earth and covering them with concrete, known as Earthships.

Some Artificial reefs are built using tires that are bonded together in groups, there is some controversy on how effective tires are as an artificial reef system, an example is The Osborne Reef Project.

The process of stamping and cutting tires is used in some apparel products, such as sandals and as a road sub-base, by connecting together the cut sidewalls to form a flexible net.

Chipped and shredded tires are used as Tire Derived Fuel (TDF); once again not recycling, but TDF helps to eliminate tires from our waste stream and produces a fuel source. Also used in civil engineering applications such as: sub grade fill and embankments, backfill for walls and bridge abutments, sub grade insulation for roads, landfill projects, and septic system drain fields

Shredded tires, known as Tire Derived Aggregate (TDA), have many Civil Engineering Applications. TDA can be used a backfill for retaining walls, fill for landfill gas trench collection wells, backfill for roadway landslide repair projects as well as a vibration damping material for railway lines.

Ground and crumb rubber, also known as size-reduced rubber, can be used in both paving type projects and in moldable products. These types of paving are: Rubber Modified Asphalt (RMA), Rubber Modified Concrete, and as a substitution for an aggregate. Examples of rubber-molded products are: Carpet padding or underlay, flooring materials, dock bumpers, patio decks, railroad crossing blocks, livestock mats, sidewalks, rubber tiles and bricks, moveable speed bumps, and curbing/edging. Then there is plastic and rubber blend molded products like pallets and railroad ties. Athletic and recreational areas can also be paved with the shock absorbing rubber-molded material. Rubber from tires is sometimes ground into medium-sized chunks and used as rubber mulch.

Ground up tires even find their way back to your car in the form of automotive parts, like: exhaust hangers, brake pads and shoes, acoustic insulation, and even low percentages go into making new tires.

Environmental Concerns

Due to heavy metals and other pollutants in tires there is a potential risk for the leaching (leachate) of toxins into the groundwater when placed in wet soils. This impact on the environment varies according to the pH level and conditions of local water and soil. Research has shown that very little leaching occurs when shredded tires are used as light fill material, however limitations have been put on use of this material; each site should be individually assessed determining if this product is appropriate for given conditions.

Ecotoxicity may be a bigger problem than first thought. Studies show that zinc, heavy metals, a host of vulcanization and rubber chemicals leach into water from tires. Shredded tire pieces leach much more, creating a bigger concern, due to the increased surface area on the shredded pieces. Many organisms are sensitive, and without dilution, contaminated tire water has been shown to kill some organisms.

United States and Local Government

US state laws and regulations dealing with scrap tires are currently enacted in 48 states. Here are some common features of state programs that deal with scrap tires: source of funding for the program; licensing or registration of scrap tire haulers, processors, and end users; manifests for scrap tire shipments; limitations on who may handle scrap tires; financial assurance requirements for scrap tire handlers; and market development activities. Some state programs are now supported by fees charged to the consumer at purchase or disposal of each tire. These fees, sometimes called ipping fees, help to support recycling costs. When the disposal rates charged to consumers are set high, this in turn discourages landfill disposal, a simple solution encouraging more affordable tire recycling programs.

References

^ U.S. Environmental Protection Agency. Management of Scrap Tires. 03 Jan. 2007. 14 Feb. 2007 http://www.epa.gov/epaoswer/non-hw/muncpl/tires/index.htm

^ Ohio Department of Natural Resources. Recycling tires. 09 Aug. 2005. 26 Feb. 2007 http://www.dnr.state.oh.us/recycling/awareness/facts/tires/

^ Price, Willard, and Edgar D. Smith. (2006). Waste tire recycling: environmental benefits and commercial challenges. International Journal of Environmental Technology and Management 6.3-4, 363-364

^ Liu,H., Mead, J., Stacer, R. Chelsea Center For Recycling And Economic Development. (1998). Environmental Impacts Of Recycling Rubber In Light Fill Applications: Summary & Evaluation Of Existing Literature University of Massachusetts

^ Price, Willard, and Edgar D. Smith. (2006). Waste tire recycling: environmental benefits and commercial challenges. International Journal of Environmental Technology and Management 6.3-4, 363-364

^ U.S. Environmental Protection Agency. Management of Scrap Tires. 03 Jan. 2007. 14 Feb. 2007 http://www.epa.gov/epaoswer/non-hw/muncpl/tires.org

^ Retrieved 20 Feb 2010 from: http://www.epa.gov/osw/nonhaz/municipal/pubs/msw07-rpt.pdf

^ 22.5 lb working figure retrieved on 20 Feb 2010 from: http://www.rma.org/scrap_tires/scrap_tire_markets/scrap_tire_characteristics/

^ U.S. Environmental Protection Agency. Management of Scrap Tires. 03 Jan. 2007. Dead Link as of 20 Feb 2010. http://www.epa.gov/epaoswer/non-hw/muncpl/tires.org

^ Price, Willard, and Edgar D. Smith. (2006). Waste tire recycling: environmental benefits and commercial challenges. International Journal of Environmental Technology and Management 6.3-4, 363-364

^ Liu,H., Mead, J., Stacer, R. Chelsea Center For Recycling And Economic Development. (1998). Environmental Impacts Of Recycling Rubber In Light Fill Applications: Summary & Evaluation Of Existing Literature University of Massachusetts

^ toxicity study http://www.ardeacon.com/pdf/Assessment_Environmental_Toxicity_Report.pdf

^ U.S. Environmental Protection Agency. Management of Scrap Tires. 03 Jan. 2007. 14 Feb. 2007 http://www.epa.gov/epaoswer/non-hw/muncpl/tires.org

See also

Vulcanization/Devulcanization

Pyrolysis

Recycle

Tire

Rubber

Tire fire

Landfill

Landfill liner

Waste Management

Artificial reef

Re-tread

Katy Trail (Dallas)

Rubber mulch

Mousepad

Underlay

Railroad tie

Rubberized asphalt

Rubberecycle

Rubber mulch

External links

Rubber Manufacturers Association (RMA)

Environmental Protection Agency (EPA)

Ohio Department of Natural Resources

Tire Derived Product Suppliers, California

International Institute of Synthetic Rubber Producers, Inc.

New Scientist article on a microwave process that turns tires back to oil.

European Tyre Recycling Association.

European Tyre & Rubber Manufacturers’ Association.

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