According to a 2003 report by the US Environmental Protection Agency (EPA), the US generates approximately 290 million scrap tires annually. Until recently, this large amount of waste has been disposed of in landfills or other types of tire piles. But with environmental legislation increasingly regarding the disposal of tires in landfills as hazardous waste, the market for alternative tire disposal methods are becoming more attractive.
The EPA believes that markets now exist for 80.4 percent of scrap tires, up from 17 percent in 1990. These markets—for both recycling and beneficial use—continue to grow.
There are various ways of recycling and/or disposing of used tires. These include the traditional landfill method; the retread and return of the used tires to market; burning tires to use for fuel; grinding tires down for crumb rubber; and punching or stamping the tire into a new product. In this article, we explore an industrial gas technology used in tire recycling— cryogenic grinding of scrap tires using liquid nitrogen to produce crumb rubber.
The market for crumb rubber, also referred to as sized-reduced rubber or ground rubber, has been growing over the past several years. According to a study by the EPA, in 2003, the US converted 28 million scrap tires into crumb rubber, or 9.65 percent of the 290 million scrap tires produced annually in the US.
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