Tyre Derived Fuel
Nearly 200 million tyres are processed into tyre-derived-fuel (TDF) chips and used in very high heat operations like cement, power generation and steel manufacturing in the US each year. North America, Europe, the UK and North Asia have been using tyre-derived-fuel to power their industries for 30 years.
Following a comprehensive review of alternative tyre disposal options in the United Kingdom, the (UK) Environmental Agency has recommended that burning tyres (TDF) in high temperature cement kilns is preferable to landfilling, from an environmental perspective. [United Kingdom Environmental Agency. 2001. Tyres Disposal Protocol.] This supports findings from other overseas investigations that show burning tyres at high temperatures does not produce unacceptable atmospheric emissions. (URS NZ Ministry for the Environment Product Stewardship Case Study for End of Life Tyres)
The tyre-derived-fuel process is quite simple. Whole passenger and even truck tyres are fed into a chipping machine which chops 12 tonnes or the equivalent of 1500 passenger car tyres into clean cut 2 or 4 inch “chips” per hour. The rubber chips are fed directly into 1 tonne bags which are then loaded into 20 or 40 foot containers. Unlike “shredding” when tyres are “chipped” the steel inside the tyres does not protrude so the chips are free flowing. When the rubber chips reach the fuel site they are fed in along with the other predominant fuel (e.g. coal, oil).
The US Environmental Protection Agency suggests properly designed existing solid fuel combustors can supplement their normal fuels with 10% to 20% tyre derived fuel and still satisfy environmental compliance emissions limits.
The aforementioned URS report states “A tyre burns completely at 650 Celsius, producing principally carbon dioxide and water…The temperature inside cement kilns, at 1800 Celsius…ensures complete combustion.” The report also says tyre derived fuel has a net calorific value of “between 26 and 34GJ per tonne, which is similar to that of common fuel sources such as coal.”
Used in a high heat facility tyre-derived-fuel actually reduces emissions by displacing low calorific value coal thus decreasing oxides of sulfur (SOx) emissions. In addition no ash is created through the burning of tyre-derived-fuel in cement kilns as every part of the tyre including the steel goes in to the manufacture of the cement.
More information on Tyre Disposal
URS New Zealand Product Stewardship Case Study for End of Life Tyres
US Environmental Protection Agency & Portland Cement Association TDF Fact Sheet