AND OF RICE LAND OF TIRES
Goodyear and renewable sources
High quality silica, comparable to the one derived from sand, can be obtained through burning rice husk. A new step in the direction of producing tires from totally renewable sources
The secret for eco-friendly tires has always been hidden in rice fields. As one of the world’s staple foods, it has spread throughout the continent - according to FAO, the United Nations Organization for Food and Agriculture - and generates large amounts of waste that can become an ecological problem. The husk, technically the hard protecting covering of rice grains, is normally sent to landfills or burned to produce electricity. From this process, though ecologically compatible, millions of tons of ashes are created, the disposal of which (as we explain in the box below) is a very important environmental issue. Cement can be produced from it, as well as silica to be used in making tire compounds. This is the path that Goodyear has chosen, the result of a constant search for new raw materials: silica is increasingly replacing carbon black, more polluting but also more economical, at least until yesterday, in new generation tires. Silica, when mixed with polymers or natural rubber, is an important reinforcing element that determines two important characteristics in a tire: grip (or road handling, especially in wet conditions) and rolling resistance (which translates in lower fuel consumption and a longer life span). Silica, regardless of its origin, reduces rolling resistance by 20% compared to a tread made using carbon black.
China forging ahead
Goodyear has already been using silica from rice husks since last September in mass production, in its Chinese factory located in Pulandian, which produces tires for the local market. The process is not new though, even if three years of research were needed to achieve the set objectives in terms of quality. As explained by both the senior director of External Sciences and Technologies of Goodyear, Surendra Chawla, and Joseph Zekoski, technical director of the Goodyear Research and Development center of Akron (Ohio, USA): "For several years, the industry has been producing silica with ashes from rice husk, but the quality didn’t meet the requirements of tire manufacturers ". Silica of plant origin, furthermore, is proving to be more economical than that of mineral origin; closing the gap, as far as production costs are concerned, with carbon black. For some time now, Goodyear has had long-standing partnerships with a number of suppliers, especially with China’s Yihai Food and Oil Industry, after an agreement was signed in June last year, to improve the quality of silica from plants. Thanks to research, silicas obtained from plants can boast identical performance compared to mineral silicas, which still represent the vast majority available on the market. According to Dave Zanzig, Director of Goodyear’s Global Material Sciences, "the use of husk improves the ecological efficiency of the production line in at least two aspects: it significantly reduces waste from the production of rice, and it requires a significantly lower amount of energy compared to producing silica from sand, since, in order to separate silica from the rest of the ashes, it is sufficient to heat the latter to 212 ° C.
Great demand, short supply
Despite the large amount of rice consumed in the world, says Surendra Chawla, senior director of Goodyear’s External Sciences and Technologies, "the supply of silica from rice husks is still very scarce. Our company has already established contacts with many potential suppliers, but for now silica from plants covers only a small part of Goodyear's needs". Other competitors (Bridgestone and Pirelli are among them, Editor's note) are following parallel processes with other suppliers. A confirmation, if ever there was a need, that the path chosen by Goodyear is the right one and is a great victory for the environment: just think of the benefits that would result if all tires (roughly one billion per year worldwide, editor's note) were made using this process.
A multitasking element
The husk is the end result of the husking or hulling process of cereals such as rice, oats and barley, an operation that separates the grain from the bracts that cover it. It makes up 17-23% of the weight of the paddy (unhusked rice). The operation is carried out mechanically with huskers or hullers, machines made up by a movable and a fixed stone or, in modern machines, by rubber-coated metal cylinders. It consists primarily of woody parts; once the rice is harvested, the husk is dispersed on the field, and since it is not used for human nutrition, being difficult to digest and for its low content of protein (4.5%) and fat (1.7%), it is then minced and used as litter for animals, poor quality forage for horses, cattle and turkeys as well as a component of artificial wood for piers or, still, as a filtering element for the production of beers. Commonly used as fuel in small cogeneration plants, its ashes make up 10-11% of the weight of un-husked rice and are rich in biogenic silica (about 90%), reused in the production of tires. Besides the rubber industry, rice husk ashes are also used in the production of Portland cement and refractory bricks for blast furnaces; they are also used by the automotive industry as the basis of the ceramic material in catalytic converters.
The quest for a fully renewable tire
Using silica from rice husks for the production of tires is just a part of Goodyear’s quest to find alternative and renewable sources like the possibility of replacing some oil derivatives with others from more natural sources. Soybean oil, in particular, could replace fossil oils in tire compounds. The research was simultaneously carried out between Akron and the European Colmar-Berg centre (Luxembourg) and showed that soybean oil can extend the lifespan of the compound by 10% compared to fossil oils, with a substantial saving of energy in the production process, and binds more effectively with the silica improving the quality of the compound obtained. Rubber itself is also the target of constant research: the aim is to reduce the dependence from natural rubber (still essential for industrial tires) but most especially from synthetic hydrocarbons. On this front Goodyear is working with a chemical giant such as DuPont Industrial BioSciences; Bio-Isoprene is the result of this partnership, which comes from biomass - and thus from renewable sources. The AMT (Air maintenance Technology) is a self-inflating system that exploits the natural deformations of the tire to let air into the tire. Cross-linked belts are also worth mentioning as they increase by 10% the maximum load of the casing compared to traditional structure as well as the recent introduction of the concept tire BHO3 unveiled in Geneva, able to generate electricity to power an electric or hybrid’s battery pack. Finally, we must not forget the "Spring tire": an air-less tire co-developed with NASA, designed to travel to other planets, and deal with the most difficult and inaccessible terrains on Earth.