The Product Guy

Dec 3 2008 10:33AM | Permalink | Email this | Comments (0) |
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By Nick Bajzek

Discarded tires have found plenty of uses: fodder for roads, race tracks, tennis shoes, playground equipment padding, and, most insidiously, in the form of a good old-fashioned tire fire.

My favorite tire fire of all time is the Springfield Tire Fire, which, according to Springfield Channel 6 reporter Kent Brockman (famous for his "And I, for one, welcome our new insect overlords" quote), has been burning since 1966—or 1989, depending on what episode you reference.

It’s the concept of the tire fire that caught the attention of the Portland Cement Association. Research released by the body supports findings from previous air emission studies conducted by government agencies and engineering firms that indicate that tire-derived fuel (TDF) use in cement kilns does not adversely affect the emissions profile of various air pollutants—in fact, using a tire fire as supplemental fuel can both make good use of a potentially dangerous pollutant and put a buffer around the staggering energy costs it takes to produce Portland cement.

As seen on The Simpsons, extinguishing tire fires is difficult. The fire releases a dark, thick smoke that contains carbon monoxide, sulfur dioxide and products of butadiene and styrene. A specific danger is posed by dripping hot fluids (which may cause burns) and valves shooting from the fire under pressure. Burning tires are heated and as they have a low thermal conductivity, they are difficult to cool down. Moreover, they frequently burn inside even if they are extinguished from outside, and easily reignite when hot.

Tyrone Wilson, Ph.D., director of regulatory affairs for PCA, said, “This study shows that tires, which pound for pound have a greater fuel value than coal, can also help manufacturers recycle tires without adversely affecting emissions. The nearly 300 million used tires generated by the United States each year can create an environmental nuisance and eyesore. By simply disposing of these tires in landfills or junkyards, society misses an important recycling opportunity: the chance to recover energy and conserve fossil fuel resources.”

The study, conducted by Air Control Techniques, P.C., is based on emission data collected by PCA from 31 cement plants presently firing TDF. The emissions of particulate matter, nitrogen oxides, most metals, dioxin-furans, and sulfur dioxide from kilns firing TDF with conventional fuels were slightly lower than emissions measured from kilns firing only conventional fuels. According to the PCA, the emission levels for carbon monoxide and total hydrocarbons were slightly higher for TDF-firing versus non-TDF firing kilns. None of these differences in emissions were significantly different.

Additionally, cement plants using TDF reduce the amount of coal burned. For each ton of TDF used, the plant reduces the need to use 1.25 tons of coal. This means that less carbon dioxide (CO2) is produced. Additionally, says Wilson, “The intense heat of the cement kiln ensures complete destruction of the tires. Because the fire is contained within the kiln under intense heat, there are no visible emissions from the tires such as the heavy black smoke seen in an open-air tire fire.”