Waste Tires: Waste or Scrap tires are made out of a material which can have no economic end use. This means that tires which are no longer suitable for use on vehicles due to wear or damage, can be recycled to serve a new economic purpose (rubber asphalt and concrete, fuel alternatives, carbon sources, etc.). [1] The United States disposes of 279 million waste tires each year, representing over 4 million tons of scrap waste. [2]
The Economic problem with tires is that the polymeric materials that they are made of, do not decompose easily. Even after heavy use and wear, only a few grams are abraded from each tire before they are deemed not serviceable. This means that nearly the entire amount of rubber is discarded, and a valuable resource is left to become an environmental pollutant, if left to be disposed of.[3] It is for this reason that waste tires must be viewed not only as an environmental issue, but also as an economic benefit.
The Disposal of Waste Tires: Waste tires are generally discarded after only a small amount of rubber is worn away. Even so, these tires are unfit for further use in the vehicles they were made for. At the same time they are also unwelcome in landfills and have been proven to be an environmental threat. Whole tires can be used for a number of applications, including artificial reefs, breakwaters, erosion control, playground equipment, and highway crash barriers.[4] Due to the sheer volume of disposable tires, they take up a great deal of valuable space in landfills. In addition, they have been known to bubble to the surface of land fills as they tend to trap methane gas. This bubbling can contaminate local water systems, as it can damage the landfill liners that are meant to control contaminants. The different stabilizers and flame retardants added to tires have also been known to kill advantageous bacteria in the soil, creating yet another economic problem. Originally, this was the primary form of disposal for scrap rubber (70% in 1977), but due to the decreasing availability of space, this process is no longer considered feasible. [5]
Since the inability for landfills to provide adequate space for tire disposal, other forms of disposal and reclamation have been put into place, using waste tires as both commodities (new tires) as well as a form of energy (fuel alternative).
_-_geograph.org.uk_-_917186.jpg)
Waste tires create problems such as landfilling, health, and environmental challenges. Accumulation of waste tires, which are non-biodegradable polymers due to the presence of fillers, steel cord, organic, and inorganic components, is a major environments concern. Different agencies in the world are now recycling waste tires and other rubber goods into useful products instead of polluting the environment. [6] In 2010 the Newfoundland and Labrador Government proposed that all waste tires in the province be shipped to Corner Brook to be burned and used as fuel. This was quickly delayed and further denied. A stock pile of waste tires that reached 1.9 million tires in 2010 was a major environmental headache for the government. Environment Minister Ross Wiseman said the Multi-Materials Stewardship Board (MMSB), a provincial agency that promotes recycling, reached agreements with Holcim (Canada) Inc. and Lafarge Canada Inc. They agreed to ship tires to Quebec where they will be burned for energy. [7]
Environmental Issues with Tire Disposal: The disposal of tires in landfills have proven to have negative effects on the environment. Not only do they take up a great deal of space within a landfill, but their process of decomposing has created a wide variety of issues that have made their disposal in landfills unfeasible and in many regions, banned. The process of bubbling of trapped methane gas has been linked to increased mosquito and other insect breeding (increase risk of disease spreading), contamination of both underground and above ground water systems, as well as chemically destroying many beneficial bacteria that grow in the soil within and surrounding a landfill. [8] Tires have been stock piled for years both legally (landfills) and illegally. In the United States alone there are about two billion around the country, with an estimated 279 million to be added to this number in the next few years. The legal stockpiling of tires increases the risk of fires which can burn for months on end, creating further pollution in the air and ground, while the illegal disposal of tires in forests, water ways and empty lots have caused pollution which cannot be regulated.[9] The most obvious hazard associated with the uncontrolled disposal and accumulation of large amounts of tires outdoors is the potential for large fires which are extremely detrimental to the environment. Once a large pile catches fire, it is very hard, if not impossible, to extinguish. [10]
The Recycling of Waste Tires: The inability of landfills to properly deal with the disposal of tires has spurred the research into ways to successfully recycle tires into commodities and resources, such as concrete, asphalt and other tires. To convert the waste tire into a valuable product, it must first be reduced in size and then recycled. The recycling process begins first by shredding tires into small manageable chips, which are then then cooled to cryogenic temperatures, causing the pieces to become brittle. These brittle pieces are then pulverized into a material that must be screened to remove large chunks of rubber or polymer. Finally, the remaining fibre and magnetic material are separated from the pulverized material using a magnetic separator and a vibrational separator. This form of recycling is environmentally friendly, and allows a valuable resource to be used again and again. [11] There is a potential for using waste tire rubber to make activated-carbon adsorbents for air-quality control applications. Such an approach provides a recycling path for waste tires and the production of new adsorbents from a low-cost waste material. [12] Also, recycled rubber from tires is used as a component of various products commonly known as "tire derived products". Such products include asphalt paving mixtures and as extenders in a variety of rubber products such as roofing materials, walk pads, carpet and flooring underlay and other products. More such products are being developed.[13]
References edit
- ^ Dodds, J., W.F. Domenico, D.R. Evans, L.W. Fish, P.L. Lassahn and W.J. Toth. 1983. Scrap tires: a resource and technology evaluation of tire pyrolysis and other selected alternate technologies. Technical Reports EGG-2241
- ^ Takallou, M. B. (1991). BENEFITS OF RECYCLING WASTE TIRES IN RUBBER ASPHALT PAVING - transport research international documentation. Transportation Research Record.
- ^ Adhikari, B., De, D., & Maiti, S. (2000). Reclamation and recycling of waste rubber. Progress in Polymer Science, 25(7), 909–948
- ^ Epps, J. A. (1994). Uses of recycled rubber tires in highways.
- ^ Adhikari, B., De, D., & Maiti, S. (2000). Reclamation and recycling of waste rubber. Progress in Polymer Science, 25(7), 909–948
- ^ Francis, R. (2016). Recycling of polymers: Methods, characterization and applications.
- ^ http://www.cbc.ca/news/canada/newfoundland-labrador/n-l-to-ship-old-tires-to-quebec-1.1064767
- ^ Adhikari, B., De, D., & Maiti, S. (2000). Reclamation and recycling of waste rubber. Progress in Polymer Science, 25(7), 909–948
- ^ Jang, J.-W., T.S. Yoo, J. H Oh, & Wasaki, I. 1998. Resources, Conservation and Recycling, 22(s 1–2), 1–14
- ^ Reschner, K. (2008, July ). Scrap Tire Recycling.
- ^ Khais, Iosif. A. Reali, M. Reali, & I. Reznik. March 6th, 1997. Tire Recycling Process. United States Patent WO/1997/007893
- ^ Lehmann, C. M. B., Rostam-Abadi, M., Rood, M. J., & Sun, J. (1998). Reprocessing and reuse of waste tire rubber to solve air-quality related problems. Energy & Fuels, 12(6), 1095–1099. doi:10.1021/ef9801120
- ^ Rutherford, D., & Recyclers, R. (1991). Patent US5115983 - Process for recycling vehicle tires.