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“Greener” compounds


Dandelion, corn, rice and even orange peel could quickly become critical components on future tires

Paolo Ferrini





Will rubber still be used on future tires? At this point, we are beginning to doubt it. Soon, what is to be considered the most important and traditional tire component, could be replaced, at least in part, by low impact materials, probably of plant origin, an eco-friendly and renewable source.

And what is more, the news that Continental has recently put into production its WinterContact TS 850 P, a new winter tire with a tread made entirely by a special rubber derived from the roots of the Dandelion (Taraxacum), has contributed to strengthen this feeling. Yes, that fluffy flower we all collected as children to blow and make a wish. Some will remember that sticky feeling on the fingers caused by the sap contained in the stem. Well, just from that milky white liquid it is possible to obtain the rubber needed to produce parts of a tire.

And since also Bridgestone, Goodyear, Michelin, Pirelli, Sumitomo, Yokohama and Apollo Vredestein have started studying the possible use of materials of plant origin, "green" tires are once again on everyone’s lips.  To tell the truth, the adjective “green” has often been abused, just as the perceived environmental friendliness of this or that product. Including tires.


Green tires! 

“Green" tires were the talk of the town already in the early 90s when Continental and Michelin unveiled their first low environmental impact car tires, made with new compounds able to guarantee a lower rolling resistance with uncompromising performance and durability. The lower energy absorbed by the tire’s rolling resistance made it possible to reduce fuel consumption as well as harmful emissions.

Continental Eco perhaps hit the market a little too soon, but Michelin Energy is still remembered for being the first to integrate silica in the tread compound.
Nevertheless, some tires soon acquired the adjective "green", which would soon be taken up, more or less justifiably, by all manufacturers. However, the road was opened, and little by little each tire brand started boasting an "eco" or "green" tire range, which announced significant progress in terms of low rolling resistance and therefore fuel consumption and environmental impact.


Bio-rubber in the spotlight 

An important turning point came when Goodyear, back in the year 2000, addressed the problem in a radical way and with the cooperation of Italy's Novamont, replaced the “traditional” carbon black and silica with a biological polymer derived from corn starch. Thus the first “bio-tire” was born, a product made, albeit partially, using a renewable source that was soon to be marketed as the Goodyear GT3.

Sometime later, during the 2010 Geneva Motor Show, Yokohama presented a tire with an innovative compound made with the use of oil extracted from the peel of citrus fruits. The result of this project was the BlueEarth, an unusual tire whose Nano Blend Compound, made up by more than 80% renewable materials such as the above mentioned citrus oil as well as natural rubber, contributed to reducing fuel consumption, while guaranteeing high levels of grip and handling at the same time. An achievement that was made possible also by the particular design of the shoulder, the reduced weight of the tire and a reduction of 3.6% in rolling resistance.

During the same event in Geneva, Goodyear too unveiled a newly developed technology, BioIsoprene, a renewable biomass that became an important alternative to petrochemical-based materials used in manufacturing synthetic rubber. Two years later, at the Paris Motor Show, it was Bridgestone’s turn to present the prototype of a tire entirely made using sustainable materials.


Russian Dandelion and Guayule 

Nowadays, Bridgestone, Continental and Sumitomo are the biggest promoters of the Russian dandelion we mentioned earlier. According to a research, performed by Bridgestone along with other operators of the sector within the PENRA (Program for Excellence in Natural Rubber Alternatives) program of the Ohio State University, thanks to characteristics that are almost identical to those of the rubber tree (Hevea brasiliensis), the Russian dandelion could represent a renewable and commercially viable option to produce high-quality eco-friendly tires, since, unlike the Hevea , the dandelion can be grown in temperate regions around the world.

Not only the dandelion, though is under the magnifying glass. Bridgestone is in fact studying the opportunity to produce natural rubber from Guayule, a perennial shrub found in southwestern areas of the United States and in northern parts of Mexico. The use of such plants would diversify sources of natural rubber for the whole industry, favoring the complete elimination of synthetic rubber. Pirelli too acknowledges the potential of the Guayule plant and back in 2013 announced a partnership with Versalis, a chemical subsidiary of the ENI group, with a view to exploiting this renewable source of materials.


Rice Husk Ash 

And it does not end here. Last June Goodyear and  Yihai Food and Oil company reached an agreement for the supply of silica obtained from the ashes of rice husks that during two tests in its Akron research center showed an impact on the performance of the tires comparable to that of traditional sources. "Sustainability is one of the pillars of innovation in our company," said Richard J. Kramer, president and CEO of Goodyear. "This new silica has numerous environmental advantages: it reduces the amount of waste to be disposed of in landfills, it requires less energy for its production and makes tires more efficient as far as fuel consumption is concerned".

According to FAO, the UN Food and Agriculture Organization, each year around the world, more than 700 million tons of rice are collected, and the disposal of rice husks is a major environmental challenge. As a result, often the husk is burned to generate electricity and reduce the amount of waste sent to landfill. Rice husk ash has been converted into silica for years, but only recently, a silica with a quality high enough to be used in tires was created.




Tires from orange juice?

The oil extracted from the peel of citrus fruit has a molecular structure similar to rubber and the two can thus be easily blended. The Super Nano-Power compound enriched by the above-mentioned oil has allowed Yokohama to obtain high performances in two seemingly incompatible areas, rolling resistance and grip, with important advantages in terms of environmental impact.

If the peel of an orange is squeezed on the rubber, for example, of a balloon, the juice that comes out softens the affected area to the point of causing it to burst. Mixing citrus oil with the polymers that make up a tire, a greater flexibility is obtained, making it therefore possible to create a compound with a high percentage of natural rubber without sacrificing grip.

Natural rubber offers less rolling resistance than synthetic polymers, but provides less grip. The addition of orange oil increases the softness of the compound allowing it to adapt to the micro-roughness of the road surface, enhancing grip. The technology described so far is based on the use of Orange Oil (Yokohama patent) and is also used on Geolander off-road tires.




Replacing Carbon Black and Silica with corn starch         

 Totally recyclable grocery bags, disposable cutleries that turn into fertilizer, baby diapers that breathe like skin, but also tires with low environmental impact. The bioplastic of the future, derived from renewable natural resources, such as corn, is a reality.

Back in 2000, Goodyear replaced carbon black and silica with a material obtained from corn starch which, despite having the characteristics of plastic, showed groundbreaking environmental performance: disposable bags, dishes and trays are completely biodegradable within a single composting cycle, while tires boast a greater rolling resistance that contributes significantly to reducing harmful emissions.

This bioplastic saves energy, helps reduce the greenhouse effect and becomes a fertile humus, since it is decomposable. Used as a filler in a tire compound, it can considerably reduce emissions of carbon dioxide (CO2).
Tires with biopolymers behave very differently from conventional ones, as they offer better performance in wet conditions and lower rolling resistance.

At high frequencies (given a temperature below 0 ° C) it displays better grip, while at low frequencies (more than 0 ° C) rolling resistance is significantly lower, which translates into a higher energy efficiency. As previously stated, another important advantage of using renewable materials such as cornstarch in the compound of a tire is the reduction of CO2 emissions.



Bridgestone looking to use Guayule                  

In early October 2015, Bridgestone announced it had successfully produced car tires with 100% natural rubber derived from Guayule. By 2020, Bridgestone will integrate sustainable materials in the production process, and in 35 years it will produce a 100% sustainable prototype.

Barbara Secchi, responsible for research on renewable materials at the Technical Center Europe in Castel Romano, says the company is considering replacing rubber with different materials including Guayule, Russian dandelion and Bio-isoprene with the aim of producing a synthetic rubber with characteristics similar to natural rubber. "There are many plants that produce rubber, but to make it industrially viable it has to be easy to extract  and available in the right quantities. The Guayule is a bush that grows in dry areas, such as Arizona. We believe it has more potential than the Dandelion, as it is more sustainable from an economic point of view.

Obtaining rubber from the Dandelion means extracting the whole plant (the rubber is contained in the root), while Guayule contains rubber in both the shrub and the root. Then there is a third way, synthetically improved poly-Bio-isoprene. We are in fact working with a Japanese company to produce bio-isoprene, the basic substance from sugars extracted from plants. However, this material shows some limitations, so we are also working simultaneously on the finished product". 

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