One of the world's biggest tire manufacturers is taking another step toward more environmentally friendly production by incorporating a byproduct created by the burning of rice husks into a material used in high-end tires.
Akron-based Goodyear is embracing a technology that converts the ash that remains from burned rice husks into silica, which has been used in tire production for two decades.
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When silica is added to a tire tread recipe, it helps reduce tires' road resistance, a phenomenon that causes vehicle engines to work harder and consume more fuel. "Low-rolling resistance" tires made with silica also grip wet road surfaces better.
Goodyear's efforts to reduce the amount of rice husk ash entering the waste stream will be modest given that between 700 million and 800 million tons of rice is harvested each year.
About 20 percent of a rice kernel is the inedible husk. Some larger rice mills have installed plants to burn husks to generate electricity, producing ash that is rich in silica.
Goodyear is working with companies in Asia to eventually process tens of thousands of tons of silica from rice husk ash.
"It's a start," said Goodyear's Surendra Chawla, senior director of external science and technology. "Hopefully it will grow over time."
Most silica for tires is produced by incinerating sand at around 2,500 degrees Fahrenheit. Chawla said rice husk ash can be converted into usable silica for tires at only 212 degrees, which he called an economic advantage.
Goodyear is not the only tire manufacturer — or industry — exploring the use of silica from rice husk ash. Dave Zanzig, Goodyear's director of global material science, said it's hoped there would be momentum throughout the tire industry to use silica from rice husk ash.
There is a concentrated effort underway in the tire industry to reduce its considerable carbon footprint. Chawla said the ultimate goal is to manufacture tires using only renewable resources.
Dan Zielinski, a spokesman for the Rubber Manufacturing Association, cautioned that while it's important that the tire industry find alternative materials for petroleum-based products, the primary concerns when making changes to tires are still performance, durability and especially safety. It can take years of research to make change, but it's key that those changes have no negative effects, Zielinski said.
Tire treads are composed primarily of natural and synthetic rubber, carbon black and oil. Those last three ingredients are petroleum-based, which has led manufacturers to explore the use of greener substitutes.
Silica, for examples, reduces the amount of carbon black — the material that gives tires their color — but increases production costs.
Goodyear has been exploring the use of soybean oil instead of petroleum products and replacing synthetic rubber with a more eco-friendly substance called BioIsoprene.
But it appears the biggest innovation for manufacturers in the near term will be production of tires that remain inflated at their proper pressure. Studies have shown that under- and over-inflated tires are the biggest cause of the road resistance that robs vehicles of fuel mileage.