Tire Recycling

Tire recycling, also known as rubber recycling, refers to the process of recycling used vehicle tires that can no longer be used on the vehicles due to wear and tear or irreparable damage. Used tires are among the most problematic and challenging sources of solid waste. This is due to their large volume, their resilience, and the fact that they contain components that pose a threat to the environment and to the people around. They also become the home ground for mosquitoes and rodents which are responsible for carrying many diseases.

It is estimated that over 250,000,000 tires are thrown away annually. Because of this high availability, resilience, bulk and non-biodegradability, tires are prime targets for recycling.

The best way to reduce the filling of tires in the landfills is to become involved in tire recycling. One of the major issue in tire recycling is the durability of tires as they are very hard to break down and therefore are seen lying in open space in large heaps.

Process of Tire Recycling

1. Collection of Used or Worn Out Tires

In every recycling process, collection is usually the first step. Here, tires are collected by individuals and some business individuals who have ventured into tire recycling business. People are paid for collecting tires and sending them to collection points. Once the tires reach the required number or volume, they are packed in huge tracks and sent to the processing plants for processing. Although it is considered a profitable venture, some people prefer reusing these used tires for other purposes at home. A good example is using the tires as rubber mulch, used in jungle gyms for strength, speed agility and resilience training.

2. Whole Tire Processing

At the processing plant, processing basically starts with cutting the tires into tiny pieces. This is an important step that aims to reduce the volume of the tires and create a material that can be handled easily. The tire shredders (the machines specially designed to shred tires) basically shred or cut tires using two counter rotating shafts which produces 2 inch pieces. The end product of this stage can be used as a raw material for tire derived fuel. Tire processing employs one of these two systems:

  • Mechanical systems
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The mechanical systems grind scrap tires into small chips using the ambient process. In a typical ambient system, the rubber shreds are put into one granulator fitted with screens that help in determination of the product size.

  • Cryogenic systems

These systems freeze tires at very low temperatures. This shutters the rubber to create different chip sizes. The tire shreds are then supper cooled using liquid nitrogen. The extremely brittle, cold rubber is then passed through a hammer mill which shatters the rubber into very tiny particles. From these tiny particles, steel is removed using powerful magnets and fibers are separated with air classifiers. Finally, clean recycled rubber is obtained and can used in other applications.

3. Steel Liberation Stage

The tire shreds obtained from step 1 are processed and prepared for the elimination and separation of the tire wire from the rubber. This important step includes fiber separation and course screening. Tires contain steel wires for resilience, strength and versatility. The steel wires are removed, recycled and sent to steel rolling mills for the manufacture of new steel. The remaining rubber can be sold as rubber mulch or can be used as playground or field turf or used as crumb rubber feed stock.

4. Screening and Milling Stage

Once the wires are separated from the rubber, the next stage is screening. This involves careful observation of the rubber to ensure there are no more wires or other contaminations. The screening process is all about screening a huge number of different sized rubbers which contain no wires, sorting them into varied sizes, eliminating all unwanted substances, and the reduction of extra-large and unwanted rubber pieces.

5. Cleaning Stage

Once the screening process is complete, the next step is the cleaning stage. Here, the rubber obtained from the screening and milling stage is thoroughly cleaned. This process involves the use of water and other cleaning agents to thoroughly clean the rubber. Once the clean rubber is obtained, it can be packed and transported to other factories that require rubber as a raw material in their processing plants. For example, rubber shoes manufacturers, playground turf manufacturers and other rubber applications.

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Some of the Tire Derived Products

Used or worn out tires have a number of uses. Although most worn out tires are burnt for fuel, scrap tires still have other significant uses as can be viewed below:

Construction Materials

An entire home can be built using whole tires by simply ramming them together filed with earth and later covering them with concrete identified as earth ships. Used tires can also be used in different civil engineering applications for example embankments and sub grade fill. They can be used for bridge abutments and as back fill for walls. Used tires are also utilized as barriers for instance collision reduction, blasting mats, rainwater runoff and wave action that protects marshes and piers as well as used as sound barriers between residences and roadways.

Used In Apparel Products

The process of recycling rubber through stamping and cutting gives large pieces that can be used in the making of sandals, or road sub-base. The prices can also be connected together to form a flexible net.

Civil Engineering Applications

The shredded tires also referred to as Tire Derived Aggregate have a number of applications in civil engineering. For example, they can be used as landfill gas trench collection walls, as back fill for road landslide repair, as vibration reducing material for railway lines and as back fill for maintaining walls.

Ground and Crumb Rubber

Ground rubber commonly referred to as size-reduced rubber, has a number of applications. For example, it can be used in paving projects or be moulded into products. Common examples of rubber moulded products include carpet padding, rubber flooring materials, patio decks, livestock mats, movable speed bumps, sidewalks, dock bumpers, railroad crossing blocks just to mention but a few.

Carbon Source

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Instead of using coke or coal in steel mills, rubber can be used as a source of fuel. In fact, studies have recommended that steel mills should adopt burning of rubber as fuel instead of coal, since coal is mined and can be depleted. Using rubber as fuel is a great way for these mills to go green and reduce their carbon fingerprints.

Impact on Environment and Health

Environmental Concerns

Due to their huge sizes and heavy metal content, tires pose a health risk to the environment and people. When put in waterlogged soils, tires can leach toxins into the groundwater and pose a huge problem.

Health Concerns

Used and dumped tires pose health problems to the people around. Insects and small animals can use the tires as their homes and later cause health issues to the human population. For example, when it rains and water is collected in the inner parts of the tires, mosquitoes can come and inhabit these places and later cause health problems to people.

In conclusion, it is important to recycle any solid waste including tires to ensure that the environment is clean.

The benefits include reducing landfills space, releases less toxic chemicals into the air, Prevent the spread of diseases which could occur by piling of the tires in the landfills sites.

References: Earth911

Image credit: vagawi
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