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. In Kuwait, the tire cemetery in Sulaibiya is so big that you can even see it from the outer space. In addition, surrounding countries are allowed to pay a fee to have their own tire waste shipped to the landfill in Kuwait. The Environment Public Authority stated that the number of existing tires range from 20 to 40 million tires .
Tires can trap methane gases posing serious fire hazards. In fact, fires outbreaks in tire landfills are common occurrences. On April 17, 2012, a fire broke out in a tire dump near Al Jahrah, Kuwait. It was reported that the fire was so big and was fueled by about five million tires . A month later another fire broke out at Amghara scrapyard. The oil they released as they burned caused an ecological disaster. The saddest part of this story is that after the fire, the landfill owners made no effort to dismantle the remaining tire piles as it kept growing each year . However, many countries in North America, South Africa and Europe have banned disposing tires into landfills and made recycling mandatory .
Figure 1. Kuwait City's Sulaibiya area tire disposal 
Figure 2. Satellite picture of the tire dump in Sulaibiya, Kuwait 
There are several amount of products that can be produced from recycling tires such as:
1. Tire derived fuel
Tire derived fuel (TDF) is made by reducing scrap tires into shreds, to burn as a fuel source . It is safe and widely recognized, including by the Federal Environmental Protection Agency (EPA). TDF is a proven technology that has been used in the U.S. for about 30 years. .In 2003, the US generated more than 290 million scrap tires nearly 100 million tires were recycled into new products and 130 million were reused as TDF in various industrial facilities. In addition, in 2017, the Australian Tyre Recyclers Association (ATRA) published a report titled “Carbon Value Proposition, Resource Recovery using Tyre Derived Fuels” noting lower emissions from the use of TDF .
To produce TDF size shreds and chips, whole tires are reduced to nominal 1-3 inch pieces using one shredder or a series of shredders, screening equipment and magnetic separation equipment. Besides size reduction, use of TDF may require additional physical processing since it contains about 30% of metal wire and fabric. Magnetic separators are required to remove the steel, depending on the type of combustion device it is going to be used for. For example the removal of the steel is unnecessary for cement kilns, since the steel replaces the iron required in cement manufacturing. However, for the pulp and paper the removal of steel is necessary as it will result in clogging the feed systems .
There are several advantages for using TDF:
The EPA recognizes TDF as an alternative to fossil fuels, producing the same amount of energy as oil and 25% more energy than coal.
TDF is less expensive than fossil fuels.
Reduces the amount of fossil fuels that are consumed.
Reduces scrap tire piles that may cause risk.
The ash residues from TDF contain a lower heavy metals content than coal.
Produces less moisture,sulfur and nitrogen emissions when compared to coal, which results in lower carbon emissions.
In cement kiln applications, the ash resulting from TDF and coal combustion becomes an integral component of the product, eliminating the landfilling of ash.
Table 1. Fuel analysis by weight 
TDF use by industry:
Cement kilns (furnaces) - 46%
Pulp and paper mills - 29%
Electric utilities - 25%
2. Crumb rubber
Crumb rubber is produced by reducing scrap tires sizes and removing the steel and fabric from the scrap tires. Two of the most common methods used to produce crumb rubber are ambient grinding and cryogenic processing. Moreover, grinding is the preferred process due to its eco-friendly nature and reasonably moderate cost . Crumb rubber can be used in an endless number of applications including rubber asphalt.
Rubber asphalt is a high performance alternative to traditional paving material. It is a mix of asphalt and recycled rubber derived from scrap tires. The mixture normally consists of 70%-80% of asphalt cement and 15%-25% of crumb rubber . Studies have established that four inch of the normal asphalt can be conveniently substituted with two inches of rubberized asphalt, to attain similar fatigue characteristics. As of right now, there are about 20,000 miles of road made from rubber asphalt and this technology is considered popular in countries like China, Brazil, Germany and Spain .
Rubber asphalt production process
Processing is required to make tires usable as a modifier or additive. The steel and fiber are removed from the tires and then the remaining tire must be reduced in size to small particles for blending into the asphalt mixture. The tires are granulated into rubber particles to various gradations passing sieve size . The rubber asphalt mixture is produced by the addition of the crumb rubber to the asphalt mixture by either the “wet” or “dry” process .
Advantages of rubber asphalt:
Rubberized asphalt have been proven to reduce noise by up to 40%-88%.
It is less expensive than normal asphalt.
It is durable and resistant to cracking, therefore it reduces maintenance costs.
It retards aging and oxidation of the resulting mixture, which increases pavement life.
Rubberized asphalt pavements have increased stiffness at higher temperatures
Can attain its initial color better than normal asphalt.
Less energy to produce rubber asphalt, which requires less aggregates (mining) and asphalt (drilling).
Prevent tire disposal; reduces waste.
Other crumb rubber products include:
Athletic surfaces and fields.
Landscape, trails and walkways.
Molded and extruded products.
Recycled rubber products.
Different crumb rubber market segments have different crumb rubber size (mesh size) requirements. Within a specific crumb rubber market, each application has its own requirements in terms of particle size and purity .
Figure 3. Mesh size range in each market category. Mesh size is a term commonly used to describe or measure the size of crumb rubber .
In conclusion, authorities in Kuwait have tried hard to deal with recycled tires. Green Rubber Recycling Co. (GRRC) by the AlMailem Group is considered a pioneer tire recycling company in Kuwait. GRRC produces rubber tiles that are recycled for diverse applications, both indoor as well as outdoor such as for playgrounds, gyms, walkways, stables, commercial and residential spaces. KISR have also Implemented a rubber asphalt project. In addition, Kuwait is also willing to use tires as fuel in Kuwait Cement Company. In April 2017, the Kuwait official environmental portal Beatona stated that Kuwait is aiming towards ‘zero landfills’ by creating recycling plants . Therefore, more needs to be done about the waste management and soon. The application of a recycled tire is a practical and ecological solution, which not only helps the environment and reduces waste but also supplies some needs within the industrial, sports and decorative sectors.
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