Q: What would it take to produce “green” tires? I understand that tires contain a large amount of petroleum products. Is there an alternative?
A: Tires are indeed no friends to the environment. Most tires on the road today are constructed of roughly equal parts natural rubber, petroleum and “carbon black” filler (derived partially from burned fossil fuels), along with a dash of other chemical additives to improve functionality. The tire industry has embraced recycling in recent years, but still some 25 percent of tires wind up in landfills, according to Michael Bloch of the GreenLivingTips.com website. Still others are incinerated, which releases benzene, lead, butadiene, styrene and other potential carcinogens into the air we breathe.
Even worse, Bloch reports, nearly half of the spent tires in the U.S. are used as “tire-derived fuel” (TDF) and burned alongside other dirty, polluting fuels such as coal. According to the Rubber Manufacturers Association, old tires fuel cement kilns, pulp and paper mills and industrial boilers, and are used as well by electric utilities and some dedicated tires-to-energy facilities.
Beyond the actual ingredients in tires, environmentalists have also been critical of the tire industry for producing tires that stick to the road so well that they cause engines to burn extra fuel to overcome the added friction, which leads in turn to more greenhouse gas emissions out of our tailpipes.
In response to such criticism, tire engineers have begun incorporating a wide range of new materials as substitutes for petroleum and chemical fillers. Today consumers can already buy low-rolling resistance tires that generate about 5 percent less friction than traditional tires. This translates into a 4 percent to 8 percent boost in fuel economy, depending upon the engine, according to Forrest Patterson of Michelin North America. Over a tire’s lifetime, that could save up to 80 gallons of gas, he says. Encouraging motorists to keep their tires inflated to proper levels has also helped reduce tire-related emissions.
What’s in these greener tires anyway? Chemically toughened natural rubbers, vegetable-based processing oils and fibers made of plant cellulose are used to replace some of the petroleum in the newer so-called low-oil tires. Meanwhile, environmentally benign silica filler (sand microparticles) has been used to replace some of the carbon black reinforcement, with the added benefit of further reducing road friction.
Japan-based Yokohama Tire now sells what it calls the dB Super E-spec car tire, which employs modified natural rubber compounds and processing oil derived from orange peels in place of much of the petroleum in traditional tires. (The company likes to brag that the dB Super E-spec is 80 percent petroleum-free.)
While greener tires are already available, tire makers have been redoubling efforts to recycle old tires into new ones to further reduce the industry’s environmental impact. Small quantities of reprocessed rubber are showing up increasingly in new tires, but manufacturers would like to see more of the 75 million or so tires Americans send to landfills get reprocessed to live another useful day as new tires or other products.
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