Landfills and Stockpiles The very properties that allow tires to be so durable with respect to wear, thermal softening, and degradation from UV, solvents and biological agents, make tires extremely resistant to reprocessing and unsuitable for landfilling. Notwithstanding their basic chemical nature, the morphology of tires is also problematic. Tires occupy a large volume although much of it is void space; when placed in a landfill, tires tend to rise to the top of the other waste material. Although cutting or shredding the tires resolves this problem, the operation represents an additional processing step and results in a waste material which does not biodegrade. Even when tires are segregated from the regular waste stream and sent to designated tire stockpiles (which sometimes reach a height of 25 meters and contain many millions of tires, (See Figure 1), they are still problematic.
The stockpiles are also problematic from another point of view: the morphology and impermeable nature of tires means that they can hold water for lengthy periods of time. Thus, the stockpiles become ideal breeding grounds for mosquitoes and rodents. For all these reasons, stockpiles are now considered public health issues. Nonetheless, it is estimated that there are approximately 10 billion scrap tires stockpiled worldwide, with about half of them in North America and roughly 3 billion in Europe. Accessibility to these tires is not always easy since many stockpiles are small and some of the tires are co-mingled with other waste in landfills. In addition to what is already stockpiled, a large number of tires are scrapped every year. It is estimated that 13 to 14 million tonnes of scrap tires are generated yearly of which 5 million tonnes are in North America, 3.7 million tonnes in Europe and 3.2 million tonnes in Asia. Alternatives to Land-Based Disposal There are currently several approaches to recycling and re-using tires rather than landfilling or stockpiling them. The main approaches can be divided into three broad categories: 1. Re-use of whole or cut tires The re-use of whole or cut tires is principally limited to civil engineering applications such as sound barriers, temporary roads, artificial reefs, etc. In some cases whole tires can be re-treaded or exported for use elsewhere (usually developing nations). The physical destruction of tires to generate powders, granulate, chips and shred is generally accomplished using mechanical force, alone or sometimes in combination with cryogenics (use of refrigerants to embrittle the rubber prior to size reduction). Principal uses for these different grades include a wide variety of consumer products (sports equipment, pigments, mats, tiles, inks, coatings, binders etc.) and civil engineering uses (roads, dams, drainage, construction fill etc.) Unfortunately, the demand and market value for the products generated from approaches (1) and (2) are not very high, and these approaches cannot be considered realistic alternatives able to solve the entire problem of waste tire management. Approach (3), the destruction of scrap tires by thermal approaches, has many sub-categories. Many different ways have been proposed for heating tires (e.g. incineration, co-combustion, pyrolysis, gasification, plasma heating, microwave heating, etc.) and all result in reducing tires to their basic components (a carbonaceous char, scrap metal, non-condensable gases, and volatile oils). The relative amounts of these fractions as well as the energy efficiency of the process will depend on the conditions and nature of the thermal destruction. However, the primary distinction between technologies based on thermal destruction is the usefulness and marketability (if any) of the products of thermal destruction. The simplest scenario is to use tires as a source of fuel, commonly referred to as Tire Derived Fuel (TDF). However, public opposition to incineration of tires (or co-combustion of tires with other wastes) is very high. More complicated scenarios involve various schemes to recover value in the streams produced during thermal destruction. Depending on the process, pyrolytic oils can be isolated and used in a similar fashion as hydrocarbon feedstock to produce heating oil, various chemicals, electricity, etc. However, these processes are complex, expensive and unreliable, and the quality of the products is often inferior to that available from conventional manufacturing operations. With respect to the carbonaceous char, many processes attempt to recover some form of carbon black, the quality of which is significantly less than that of virgin carbon black, limiting its value and market demand for re-use in rubber manufacturing. Other options include the sale of scrap steel (not a large income stream) and the combustion of various streams for heat generation within the plant. Thermal processes proposed to date have had difficulties with process efficiency and cost, recovery of value from product streams, and even procurement of a stable supply of tires. Despite tipping fees for the tires entering, these plants have for the most part been unable to make the transition to viable business operations. Contact CBp Carbon Industries |
CBp Carbon Industries Acquires Stake in Leading Pyrolysis Firm and Strengthens Management CBp Carbon Industries Inc. is pleased to announce that, as part of a strategic alliance, it has purchased a 12% interest in Terragon Environmental Technologies Inc., believed to be the world's leading company in pyrolysis technology and research. Breakthrough Nanotechnology Process for Recycling Tires Selected by EU Recycle Tire Program CBp Carbon Industries Inc. breakthrough nanotechnology allows automotive industry to meet EU directives for recycling tires and would also reduce 40,000 tonnes of carbon dioxide greenhouse gas emissions per facility. EU Recycle Tire Test Results Announced CBp Carbon Industries Inc. breakthrough nanotechnology allows automotive industry to meet EU directives for end-of-life scrap tires and would also reduce 40,000 tonnes of carbon dioxide greenhouse gas emissions per facility.
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Tire stockpiles are a major fire hazard. Once tire fires begin, (through natural causes or arson) they are extremely difficult to extinguish. Stockpiles containing millions of tires have been known to burn for many months (See Figure 2). These fires create toxic gases, particulate-laden smoke, and contaminate the ground and water.