There’s dirty manufacturing, there’s dirtier manufacturing and then there’s vehicle tire production. The manufacturing process releases toxic emissions into the air, including volatile organic compounds (VOCs) and soot, discharges toxins into water treatment plants and produces large amounts of waste products that contain solvents and other harmful substances. After a tire’s useful life is over, it is sent to a toxic landfill. Used tires produce a landfill blight like few other products.
It has been estimated that, depending on their type and size, somewhere between four to 10 gallons of petroleum to produce. Given their reputation for eco-villainy, tires are unsurprisingly a target of green-and-clean innovation in recent years. While making a truly green tire may be years away, some companies have made strides in manufacturing more ecologically sustainable tires.
Improving Tire Efficiency
Interestingly, the biggest ecological damage by tires comes not from their manufacture or how they are disposed but what they do not do. A few years ago, Scientific American reported on the activities of a group of tire industry researchers who analyzed a tire’s total life cycle from an ecological perspective. They found that 86 percent of a tire’s negative ecological impact did not originate from its materials or manufacture but rather the extra fuel burned by a car to overcome the natural resistance that rubber has when rolling on pavement. In fact, about 25 percent of the pollution produced by a vehicle resulted from the car’s need to work to overcome the tires’ rolling resistance.
Based on this research, many tire companies realized that making tires out of greener materials wasn’t necessarily the answer to eco-friendlier products; it was making them roll more easily. Several companies began looking at using substances that could lower friction. A reduction in friction of just 5 percent could help improve a car’s fuel economy by 4 to 8 percent and lower the lifetime emissions of the car.
Some manufacturers found that by adding precipitated silica to tread formulations, they could boost tire efficiency and bring down rolling resistance, or the amount of energy required to turn the tires, according to PPG Silica Products. This would, in turn, decrease fuel consumption.
Precipitated silica, a synthetic form of silicon dioxide used in manufacturing in a powder or granule form as a reinforcing filler in tire treads, has been found to lower rolling resistance by about 30 percent. It has been estimated that if precipitated silica were used by all tire manufactures, it could save the United States about 8 billion gallons of fuel each year, translating to about $32 billion in fuel cost savings and about 45 million tons of carbon-dioxide emissions.
While silicas aren’t new to the tire industry – it has been known for a long time that silicas used in the manufacturing process can help tires grip roads better under adverse weather conditions and improve wear and tear – up until recently, it was used sparingly because it drove up costs and complexities in the manufacturing process and lowered tread wear. In the the early 1990s, highly dispersible silicas emerged, making the addition of silicas to tires more feasible.
Greener Materials for Tires
Moving forward, Americans are increasingly likely to find themselves driving on tires made from plant materials.
While manufacturers strive to make tires more efficient, there is still a need to make them less toxic, and the silica additions can help. In experimenting with low-rolling resistance tires, researchers found they were inadvertently making tires greener, since they were replacing many of the petroleum-based substances traditionally used in tire construction, Harold Herzlich, president of Herzlich Consulting and a former tire industry executive, told Scientific American.
In other words, if the traditional substances used in tire manufacturing are more resistant to rolling, then it was time to consider reformulating the existing petroleum-based materials and find better alternatives, including renewably sourced raw materials. These greener materials include natural rubbers, vegetable-based oils and cellulose from plant fibers, all of which forward-thinking tire companies are experimenting with currently.
One company is Pirelli Tire, which has begun to build a greener reputation (the company invests 7 percent of its revenue in green R&D). The company runs a UK development center, where it is currently working on a new line of eco-tires using both its own money and several million British pounds in grant money from the UK’s Regional Growth Fund.
Pirelli has built new process machinery to serve its more eco-friendly tire manufacturing, which will ultimately lead to development of a range of low-carbon emission tires that will both need less energy to manufacture and improve fuel efficiency by reducing rolling resistance, according to the UK website TyrePress.
Another manufacturer, Japan’s Sumitomo Rubber Industries, has already helped launch a Dunlop-branded tire line called Enasave 97 that uses more renewable ingredients. It plans to introduce a zero-petroleum-based tire next year.
The company not only added silicas to lower rolling resistance, but also added a modified natural rubber designed to grip better, as well as a vegetable-derived processing oil and cellulose-based (rayon) casing fibers, according to company spokesperson Masatoshi Hayashi. The prototype Enasave tire, which was introduced in 2008, contained 97 percent natural compounding ingredients; the company’s next goal is to create a tire that contains no petrochemical materials.
Another Japanese tire manufacturer, Yokohama Tire, is developing tires that are about 80 percent petroleum-free, using modified natural rubber and an oil derived from orange peels, a high-volume waste product of the global orange juice industry. Other companies have experimented with using natural latexes derived from sources as unlikely as Russian dandelion and guayule, a shrub that grows in desert areas of the U.S. and Mexico.
Step one is to make a tire that rolls better. Step two is to make a tire using less toxic materials. Step three is to extend a tire’s useful life by reusing it after the original life cycle. Globally, by volume, tires are some of the most prolific contributors to toxic consumer waste.
There have been a number of innovative ways to use tires in recent decades. In fact, today, tires are one of the most reused waste materials on the planet. They regularly find their way into new tires, athletic shoes, gym floors, asphalt, Portland cement, garden mulch, playground cushioning and even green building materials.
A European technology developed in the 1990s that allowed old tires to be remolded into airplane tires has been adapted for producing “like-new” automobile tires. The process involves removing the old tread, cleaning and buffing the tire at high speed, and then applying new treads that contain high levels of silicon carbide granules, followed by remolding and rebalancing. This, in effect, makes the tires better than they were originally and reduces to near zero the amount of petroleum products used in manufacture.
With continuing advancements, manufacturers will be able to drive toward green consumer tires into profitable new ventures. In the meantime, remember to keep your tires fully inflated.