Where does the tire fire myth come from?
You know how much I dislike when tire recyclers make use of tire fires and mosquito breeding as motivation for their recycling solution. Some industry friends even put tire fire images into their presentations just for me!
My dislike is not because I believe that those are urban myths (which they are), but rather because it shows that these companies do not understand their markets.
Push marketing is so inferior to pull marketing. It is much easier to pull customers to your product if it serves an ecologic and economic purpose in their application.
What could have started the tire fire urban myth?
In the 1980ies, an opportunistic businessman started hauling old tires at 25 cents a piece at Snohomish Riverside in Everett, Washington, USA. Over time, more than 4 million tires (some 32,000 metric tons) piled up in the dump (tire dump millionaire, anyone?). Arsonists ignited the tire mountain, which burned from September 1984 to May 1985. Yes, the fire burned for NINE months, releasing toxic materials and a lot of smoke.
Some speculate that this Everett tire mountain fire inspired the creator of The Simpsons sitcom, Matt Groening, to create the "Springfield Tire Yard Fire" in the popular sitcom, which was first shown on November 3rd 2013 in "Four Regrettings and a Funeral". Matt's mother, Marge Wiggum, grew up in Everett, but Matt was born in Portland, Oregon.
(Sources: liveineverett.com, en.wikipedia.org)
Both fires, the real tire fire in Everett as well as the cartoon tire fire in The Simpsons were attributed to have been ignited by cigarette ash.
But tires do not ignite with cigarette ash
Due to the lack of volatile combustible material in the rubber, tires need about 10% weight of a secondary combustible fuel (e.g. petrol) to generate sustained heat for at least 15 minutes before they will ignite. This is kind of comparable to igniting BBQ charcoal.
The drama starts when tires actually burn. Due to the dense rubber material, tires can only burn on the outside surfaces where oxygen can access. The flame cannot penetrate deep into the rubber because oxygen cannot permeate that deep. This means that the heat generated at the outside starts an oxygen deprived pyrolysis process at the inside of the rubber, converting rubber material into gases including methane, gooey heavy oils and char. Some sources report explosions and fire jets due to the release of gases trapped within the tires.
So, you will need tires AND lots of petrol to THEN ignite tires with cigarette ash
There might be mindless accidental cigarette ash falling on tires, but to really ignite tires, you need petrol and (drumroll) intend. Tires only ever burn with intend by arson. Tires, despite their high content of petrochemical materials, do not burn by accident.
This kind of undermines the argument that tire recycling prevents toxic tire fires, does it?
There have been arson tire fires even at faithfully and safely operating mechanical tire recyclers. These recyclers now are obliged to store end-of-life tires in small separate piles in order to better control keep potential fire hazards.
A tire fire, as bad as it is, does not help you sell your tire recycling technology.
End of story. Thanks for reading!
