Not so long ago, there was a concern about what to do with truck tires once they could no longer be retreaded or repaired. Today, most of the new practices should make our industry proud. It’s taken the North American economy a while to figure out the scrap tire dilemma, but as usual, it appears we’re finally getting it right. The issue is large—approximately 4,406,000 tons of scrap tires were generated in the U.S. during 2013, according to Factbook 2014: U.S. Tire Shipment/Activity Report by the Rubber Manufacturers Association. The industry has been focused on possible alternatives of recycling, although the economics have proven difficult.
For starters, recycling tires requires accumulating large volumes in concentrated locations, and scrap tires are not exactly high-value freight. Collection sites are not welcomed in many communities where memories of scrap tire fires are still alive. The fees collected for scrap tire disposal, today, goes toward transporting them to high-volume processing stations. In the past, some of the disappointing local use included playground cushions (this requirement is so small it is negligible), asphalt type road pavements mix (more “flexible” rubber containing roads deteriorate fuel economy through increased rolling resistance), and artificial ocean reefs used for fish breeding or species protection. A wide variety of potential uses have been explored but have proven largely unsuccessful.
A bright spot has been the recognition that tires contain more BTU energy per pound than good quality coal and, therefore, can be used as a high energy fuel source. Further, burning tires creates no toxic waste, in part because tire fires burn at high temperatures. Therefore, special containment burn areas are necessary such as those used in cement kilns, brick manufacturing and specially constructed electric utility boilers. Some pulp and paper mills are also good candidates. These four industries currently account for 95% of all scrap tire derived fuel (TDF) consumption. Specialized tire burning facilities recognize that tire fires are difficult to start and equally difficult to stop. Therefore, a continuing supply is desirable to avoid switching to alternative fuel sources. Most tires used for TDF are not burned whole, but instead are cut into small pieces approximately one to 2 in. long to expose additional surface area for combustion. The steel ply, belt, and bead materials are culled out and recycled separately.
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Improved retreading of commercial truck tires has greatly diminished the scrap tire issue over the last two decades. Technology that extends the life expectancy of new tire casings and the consolidation of retread processing from many small shops to fewer large operations controlled by new tire manufacturers are the primary reasons. Most retreads have tread pattern designs, rubber compounds and curing processes that make them close to their new tire counterparts in performance areas such as treadwear and fuel efficiency.
Retreading makes sense for several primary reasons. First, retreaded tires cost less than new tires and keeping casings in service longer lengthens new tire cash flow intervals.
Resource conservation is also attractive. Each new 22.5 in. linehaul type radial tire requires approximately 22 gal. of oil to manufacture. This is a combination of petroleum based materials in the tire and processing energy. Retreading that same used casing requires only seven gal. of oil, saving 15 gal. of oil for each retread. Since commercial truck tires now account for less than 40% of the total tires scrapped annually, the majority of tires available for conversion to TDF are passenger and light truck models.
One especially interesting statistic is that, as late as 1990, about a billion scrap tires were scattered across the U.S. in stockpiles. By 2013, about 92% of those tires had been cleaned up. Therefore, we are approaching the point of having the supply of scrap tires available for conversion to TDF being equal to the demand.
Today, approximately 80% of the remaining scrap tires are located in only four states. Most states prohibit scrap tires in dumps and landfills (they have a habit of rising to the surface over time) and nearly all have tire storage/disposal regulations on their books. For more information on the scrap tire issue, see the Rubber Manufacturers Assn. website.
This group researches and publishes a detailed report every two years. Their 2015 report should be available later this year.