Few consumer products have a poorer environmental image than the car tire. It is hard to escape the bleak sight of coal-colored mountains of used tires that blight the U.S. landscape. But like other parts of the automobile, the tire has been partially reworked during the past decade to make it more ecologically sustainable. As a result of efforts by tire industry chemists and engineers, many of today’s tires roll more easily to save fuel and contain fewer petroleum-based ingredients, both of which shrink this difficult technology's carbon footprint. The work to green the tire further will continue.

When global climate change began to grab headlines some years ago, tire industry researchers analyzed the car tire's total lifetime ("wells-to-wheels") environmental impact to help determine how it might be improved. They found that the aspect of the tire that contributes the most to greenhouse gas emissions—around 86 percent of its effect—is related to the amount of the extra fuel that tires cause engines to burn to overcome the rubber's resistance to rolling, says Forrest Patterson, technical director for passenger cars and light truck tires at Michelin North America in Greenville, S.C. Every 3.8 liters (gallon) of oil that remains unburned keeps 8.2 kilograms (18 pounds) of carbon dioxide out the air.

Tire companies responded initially by developing low rolling resistance tires that generate about 5 percent less friction as they rotate on the pavement, which can boost fuel economy by as much as 4 to 8 percent over regular models. Over the lifetime of a tire, "we could be talking about saving from 10 to 80 gallons [40 to 300 liters] of gasoline" this way, Patterson says. They also set about encouraging motorists to maintain full inflation pressures.

But now tire-makers have turned increasingly to finding renewably sourced raw materials to replace current oil-based ingredients of tires. Depending on the model, anywhere from 15 to 38 liters of petroleum are required to produce a standard tire. Low-oil content tires use various natural, sustainable ingredients as substitutes including chemically toughened natural rubbers, vegetable-based processing oils and fibers made of plant cellulose. They also found nonpetroleum versions of what the tire industry calls fillers—special functional additives that boost, for example, manufacturing processability or durability.

Tire chemistry is more complex than one might expect. "Some 30 or 40 chemicals go into tire rubber compounds, depending on the component—tread, sidewalls, belts, carcass plies and liner," notes James Rancourt, a consulting polymer scientist who heads Polymer Solutions in Blacksburg, Va. By weight, he explains, the tread compounds of a conventional tire contain about 28 percent natural rubber, which comes from latex sap, 28 percent synthetic rubber, which is made from oil, and 28 percent carbon black filler—a sootlike reinforcing agent that is produced by partially burning fossil fuels. The remaining 16 percent comprises different functional agents of various kinds.

The drive to produce low-rolling resistance tires was, in fact, a first step toward making them more ecofriendly because it involved replacing certain petroleum-based substances in tire construction, says Harold Herzlich, president of Las Vegas–based Herzlich Consulting, a former tire industry executive. Manufacturers added modified silica filler—essentially, surface-treated sand microparticles—to replace some of the carbon black reinforcement in standard tires. It lessens the frictional heat that the rubber compound creates as it flexes, stretches and recovers with each turn.

Japan's Sumitomo Rubber Industries introduced several years ago a Dunlop-branded tire line called Enasave 97 that incorporates natural ingredients. Sumitomo engineers not only used silica fillers, they also employed a specially modified natural rubber that grips better than unmodified versions, along with vegetable-derived processing oil, and cellulose-based (rayon) casing fibers, says company spokesperson, Masatoshi Hayashi. In 2008 it unveiled a prototype Enasave tire that contained 97 percent natural compounding ingredients and plans to market a model that will contain no petrochemical materials at all by 2013.

8 Comments

1. 1. zziizzii 10:00 AM 8/11/10

   dose any one know what do "vegetable-based processing oils " mean ??

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2. 2. SciAmISAwesome in reply to zziizzii 02:49 PM 8/11/10

   Oils are hydrocarbons, and hydrocarbons can come from fossil fuels (coal, natural gas, etc.) or from sustainable sources like plants and even animals. A vegetable-based oil will be an oil derived from vegetables instead of from fossil fuels.

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3. 3. jerryd 10:09 PM 8/11/10

   I'd rather have a good low rolling resistance tire as opposed to a low oil tires as most of the oil used is the dregs of the refining process which isn't worth much and very dirty to burn. They were paying until recently to get rid of the Petro-coke used to make carbon black it was so worthless.
   
   In my EV's I use low rolling resistance tires and they give me about 15% more range. But anyone can get better mileage by running the max pressure your tires can handle and they still handle ok. So test them, handling, braking after pumping them up to make sure nothing bad happens. If the car uses different pressures front to rear, keep that ratio when increasing pressures . And watch for wear in the center. If it gets noticeable, cut the pressure back some. But doing this can give 10% better mileage on many cars.
   
   Add that to driving so you brake much less by giving good room between your car and the one in front and take your foot off the gas when you first see the light turn red, ect can increase mileage by 30%. Not bad for a little extra pressure and safer driving.
   
   Then when getting new tires, get LRR ones.

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4. 4. Tan Boon Tee 10:42 PM 8/11/10

   It is wonderful to have smart and eco-friendly tires.
   
   But can one have puncture-proof tire, like bullet-proof vest? That would help to eliminate one of the worst hassles in driving -- unless of course, the cost has been impossibly steep.

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5. 5. joedokes in reply to Tan Boon Tee 01:06 PM 8/12/10

   There is no such thing as a "bullet proof" vest, kevlar and other materials are bullet resistant, thus a big enough bullet will puncture a "bullet proof" vest. This is why the body armor industry now refers to them as body armor, or bullet resistant vests.
   
   On a side note, tires have incorporated a number of puncture resistant technologies for over thirty years. First with woven steel belts and recently with woven kevlar belts. Yes the same stuff as body armor.
   
   Modern tires are one of the most reliable components on your car. High quality tires can last 60,000 miles. As far as flats go, I've only had 1 flat in the last ten years, and that was on a five year old heavily worn tire.
   
   Regards,
   
   Joe Dokes

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6. 6. Neptunerover 06:26 AM 8/20/10

   There already are known ways of achieving anti-gravity, and the tire industry is a strong opponent, which figures. That which is good for man and the planet is not good for business.

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7. 7. eco-steve 12:12 PM 9/8/10

   Back in the early eighties, the french car manufacturer Citroen patented a technique to convert tires into fuel using pyrolysis. They never applied it, because of death threats to their staff....Now just who do you think was responsable for the blackmail? Could it have been a fuel producer? And the technique to recycle tires has still not been applied! So they still provide breeding grounds for mosquitoes and malaria in shanty town dumps.....Ah! the joys of the free market!
   

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8. 8. Rich213 in reply to eco-steve 06:47 AM 9/14/10

   Your comments of death threats preventing the use of new technologies, is similar to the "50 mpg carburetor" of the 1920's. Oh-- how these stories have such long lives.
   Tires are being recycled, once shredded into filler for road surfaces and many molded products. The free markets are using recycled materials because they are very cost effective, but I guess that this does not fit your "bad guy" image of free markets.

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