Globally, about 4 billion tires end up as solid waste each year. Since tires are highly un-degradable, if not properly disposed they can remain in the environment for up to 100 years. There are three main categories for recycling scrap tires - mechanical, chemical, and thermal. Mechanical recycling involves reusing tires as whole or shredded pieces. Chemical recycling breaks tires down into materials like chemicals and fuels through processes like devulcanization. Thermal recycling recovers energy from tires through burning.

1. Waste Recycling & Utilization
~ Waste Tires ~

2. Waste Tires
Automotive tires are made of synthetic rubber which
is obtained from petroleum. The development of tires
was based on improving the performance of natural
rubber which is obtained from the liquid latex
secreted by certain plants.
Tire Structure & Composition
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“Rubber tree” Hevea brasiliensis

3. Waste Tires
Globally, it is estimated that 1.5 billion tires are being produced every year,
and about 4.0 billion tires end up to solid waste streams, which represent a
potential hazard to the environment. Since the waste tire has highly un-
degradable properties, without its proper disposal, the tires waste could
remain in the environment up to 100 years
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4. Recycling of Waste Tires
The recycling of scrap tires can be done under different categories:
 Mechanical: Using the scrap tires as whole or mechanically modified
shapes (in crumps or shredded).
 Chemical: decomposition or separation of scrap tire contents into
different materials (such as chemicals & fuels).
 Thermal: energy recovery
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5. Recycling of Waste Tires
Mechanical Methods:
 Reuse
Innovative uses of scrap tire
(a,b,c) road sub-layer
stability,
(d) tire pieces as fill
material,
(e) slope stability,
(f) ship bumper at warf.
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6. Recycling of Waste Tires
Mechanical Methods:
 Size Reduction
Nearly all processors first shredded the scrap tire into chips, mostly 2” in
size. By shredding, the volume of scrap tires can be reduced to about ¼,
thus reducing space requirement and shipping costs. At the same time, tire
chips are easier to handle with standard equipment.
 Secondary granulators
 High speed rotary mills
 Extruders or screw presses
 Cracker mills
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7. Recycling of Waste Tires
Mechanical Methods:
 Ambient Tire Recycling
7 Example scrap tire recycling system (courtesy of CIMP France).

8. Recycling of Waste Tires
Mechanical Methods:
 Cryogenic Tire Recycling
This process is called “cryogenic” because whole tires or tire chips are cooled
down to a temperature of below –80 C (-112 F). At this temperature, rubber
becomes nearly as brittle and glass and size reduction can be accomplished by
crushing and breaking. This type of size reduction requires less energy and
fewer pieces of machinery. Another advantage of the cryogenic process is that
steel and fiber liberation, is much easier, leading to a cleaner end product.
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9. Recycling of Waste Tires
Mechanical Methods:
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Comparison between Ambient and Cryogenic Processing

10. Recycling of Waste Tires
Mechanical Methods:
Applications of tire rubber crumbs
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11. Recycling of Waste Tires
Chemical Methods:
Devulcanization
Devulcanization means reverting
rubber from its thermoset, elastic
state back into a plastic, moldable
state. This is accomplished by
severing the sulfur bonds in the
molecular structure. With the proper
devulcanization method, a much
higher percentage of crumb rubber
old tires can be used as
compounding.
Devulcanisation methods:
 Thermal reclaim process
 Mechanical devulcanisation
 Devulcanisation with microwave
& ultrasound
 Chemical-based devulcanisation
 Bacterial devulcanisation
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12. Recycling of Waste Tires
Devulcanization
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Thermal devulcanization
Microwave-assisted devulcanization
Ultrasonic-assisted devulcanization
Mechanical devulcanization

13. Recycling of Waste Tires
Devulcanization
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Bacterial devulcanization
Chemical-based devulcanization

14. Recycling of Waste Tires
Thermal Methods: Chemicals, Fuel & Energy Recovery
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