The three Rs of eco-friendly tires: Raw materials, rolling resistance and recycling

There’s great news from some of the world’s biggest tire companies – Bridgestone Group (Bridgestone and Firestone), Michelin, Goodyear, and Continental – about the future of eco-friendly tire technology. All now have programs in place that are advancing the quest to end the use of fossil resources in tire manufacturing and make tires completely from sustainable materials. Bridgestone’s stated goal is to make tires from “100% sustainable materials” by the year 2050.

But what exactly does the term “eco-friendly” mean when applied to tires? Basically, “eco-friendly” means anything that is not environmentally harmful – a pretty broad definition. The eco-friendliness of a complex manufactured product like tires includes the environmental effects of the tire manufacturing process, the environmental impact of the tire during its life, and the effect on the environment of the disposal of the tire once it has reached the end of its useful life. So in order to examine the eco-friendliness of tires, we must first look at the three Rs of eco-friendly tire technology – Raw materials, Rolling resistance, and Recycling.

Raw materials

Among the essential raw materials used in tire manufacturing, synthetic rubber, carbon black, reinforcing fibers, and rubber compounding agents have been singled out as primary targets for improved eco-friendliness. Bridgestone has successfully created synthetic rubber using plant-derived materials rather than the usual petroleum products. Other companies are also experimenting with producing synthetic rubber made from biomass (plant-derived material or agricultural waste).

Continental, Michelin, and Goodyear are also seeking substitutes for natural rubber, so they can reduce the environmental impact and logistical expenses of importing natural rubber from subtropical countries. Russian dandelion and Guayule plants have been found to have many of the same qualities as natural rubber. The plants can be grown in Europe and the United States as sustainable raw materials and harvested more cost effectively than rubber trees. These tire companies now have experimental farms in various parts of the world, dedicated to the development of a commercially viable, eco-friendly manufacturing process.

Experiments by Goodyear show that soybean oil has great potential as a natural ingredient in tires – increasing tread life by 10% and reducing the use of petroleum-based oil by up to 8.5 million gallons per year.

Tire companies are also looking for a sustainable substitute for petroleum-based carbon black, which is used as a tire pigment and also to conduct heat away from the tread and belt areas of the tire. Experiments are being conducted to make carbon black from intermediate materials with biomass ingredients, such as vegetable fats and oils.

Russian dandelion roots photo by Thomas Ondrey, The Plain Dealer

Guayule photo by D'Lyn Ford, New Mexico State University

Rolling Resistance

Rolling resistance is the energy a tire consumes while rolling under a load. The lower the rolling resistance, the less energy it takes to move your car along the road. This translates into improved gas mileage and reduced CO2 emissions into the environment. The energy consumed by your tires’ rolling resistance can be significant. According to the Alternative Fuels Data Center, an estimated 5% to 15% of passenger car fuel consumption is used just to overcome rolling resistance.

Low rolling resistance (LRR) tires have improved significantly over the past several years, and the technology has advanced to the point where these eco-friendly tires also offer good all-around performance. Virtually all major tire manufacturers now offer LRR tires, but do your research carefully before you buy, as there are no mandated reporting standards for tire rolling resistance. Tire manufacturers apply their own rating systems and comparing different brands may require some careful reading.

Recycling

Vulcanization is the process of heating and hardening rubber compounds to make them serviceable. Vulcanization was discovered by Charles Goodyear way back in 1839, yet it’s still the foundation for today’s tire manufacturing processes.

Worn-out tires can be used for many purposes, including tire-derived fuel, civil engineering applications, and ground rubber applications. But unfortunately, the transformation of the rubber brought about by vulcanization made it impossible to recycle used tires and retrieve the raw materials to make new tires.

Until now.

Goodyear has patented a highly promising process for devulcanizing cured rubber. Although it’s still being tested, the process initially resulted in a 40% material recovery rate and has now been improved to a recovery rate of 80%. This is pretty impressive when compared to other devulcanization processes, which only deliver recovery rates of 1 - 2%. If the new process can be scaled to commercial size, it could offer a viable solution to the recycling of more than 800 million scrap tires in North America and provide a means of increasing the recycled content in new tires.

Serious strides have been made in laying a foundation for manufacturing increasingly green, eco-friendly tires. Thanks to the commitment of tire manufacturers, we can envision a future where tires will have less and less of a negative impact on the environment.