Landfills waste tyres

In the past, landfills have been the preferred method of waste tyre disposal because burial eliminates the fire hazard associated with above-ground storage, as well as the unsightliness of tyre piles. However, problems with this method have become increasingly apparent. Because of their composition, tyres are neither decomposable, nor can they easily be compacted (Blumenthal 1993). Therefore, tyres occupy large volumes of landfills, contributing to the already prevalent problem of landfill crowding. 

Several approaches have been made to reduce the number of landfilled, stockpiled, or illegally dumped tyres. Markets now exist for about 78% of all waste tyres (Fig. 3a), up from 34.5% in 1990 (Blumenthal 1993). These markets continue to grow due to innovative approaches, which include improvements in design and material to increase the lifetime of a tyre, as well as various alternatives to tyre disposal (Table 2). 

The most obvious advantage to using tyres as a fuel source is the partial alleviation of many of the environmental problems associated with traditional disposal of scrap tyres in stockpiles and landfills. The eradication of tyre piles and landfill waste will reduce many of the risks to human health linked to the buildup of tyre waste. The removal of outdoor tyre stockpiles provides great aesthetic benefits as well. 

Looking more closely at the fate of tyre waste in the USA, it was estimated in 2011 [5] that only around 10% was being recycled into new products, with over 50% being burned for energy recovery (e.g., tyre-derived fuel (TDF) oil) and the rest being discarded into landfill and so on. With respect to the proportion of tyres that are placed into landfill worldwide, a recent estimate has put this at 25% of the total number of waste tyres [6]. 

Shredded tyres can be used in the construction of landfill sites as a replacement for other construction materials. The areas that they are used in include lightweight backfill in gas-venting systems, leachate collection systems and operational liners. Shredded waste tyres can also be used to cap, close or daily cover landfill sites [75]. Their use as a backfill material and cover material can be more cost-effective than the use of other fill materials, as they can be shredded on site rather than being transported in for that particular purpose. 

Considerable attention has been paid over the last few years to the use of microwave pyrolysis for the processing of scrap tyres. Approximately 2.5 million tonnes in North America, 2.0 million tonnes in the European Union and 0.5 million tonnes in Japan, of scrap tyres are discarded per year. As much as 50% of this waste is landfilled which is clearly causing an increasing unsustainable and unacceptable situation. Other recycling... 

Equally important although not publicised at the time was the accumulation in large dumps of discarded vehicle tyres. These are in fact much more persistent in the environment than plastics and secondary uses have been traditionally found for a proportion of discarded tyres, ranging from impact absorbing buffers on boats and docks, to recreational usage in childrens play areas. Durability has been turned to advantage in these secondary applications of used tyres but in practice they utilise only a small fraction of the polymer wastes and a major proportion of discarded tyres ultimately end up in landfill. 

The Identification of Non-Hazardous Secondary Materials That Are Solid Waste rule published by the US Environmental Protection Agency (EPA) in 2012 determines whether non-hazardous secondary materials are considered fuels or wastes when burnt. Combustion units that burn non-hazardous secondary materials that are classified as fuels are regulated as boilers under Section 112 of the Clean Air Act, while units that burn materials that are classified as wastes are regulated as incinerators under Section 129 of the Clean Air Act. In the rule, the EPA identified two secondary materials (resinated wood and scrap tyres managed under the oversight of the established tyre collection programmes) as non-wastes when used as fuel, and also identified off-specification tyres managed under the contractual relationship as non-waste fuels. However, scrap tyres that are discarded in stockpiles, landfills or monofills will be considered wastes unless these tyres are processed as specified in the rule. 

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