The tire industry has come a long way from rubber tree sap tires, but researchers say that a return to plant-based rubber components is a good option for the tires of the future. According to the NY Times, regular synthetic rubber tires are made using five to 10 gallons of petroleum ingredients — an inefficient recipe for a carbon footprint disaster. The Times says that car manufacturers have made headway in terms of sustainability (they've cut emissions, used water-based paint, etc.) but they need to step up research and development for eco-friendly tires.
The article emphasizes the crucial importance of fuel efficiency in tires, which "result[s] from reducing their rolling resistance ... and ... by assuring that proper inflation pressures are maintained." In other words, a tire made from green materials does no good if it doesn't maintain or improve the fuel economy of the car.
The Times quotes Forrest Patterson of Michelin North America, stating, "85 percent of the tire's environmental impact revolves around how it affects fuel consumption," and "only 12 percent of the carbon dioxide emissions associated with tires arise from the raw materials and manufacturing." Which is why many manufacturers have focused their efforts to the shape and design of the tire, using mineral fillers and other innovations to reduce friction.
But many manufacturers are starting to return to the idea of naturally occurring rubber to reduce the petroleum content found in the tires. According to the article, Goodyear and partner Sumitomo Rubber Industries first created a "green" rubber tire in 2006. That tire cut the synthetic rubber content in half and used modified natural rubber, which provides a good grip in hard driving. The tire, named Enasave, used vegetable oil and plant cellulose instead of petroleum. The company is working toward a 2013 goal of marketing a 97-percent nonpetroleum tire that uses "no petrochemicals at all."
Other companies, like Yokohama Tire, have similar goals. Yokohama is using orange-peel oil repurposed from fruit juice factories. The Times says this tire reduces friction by "about a fifth over conventional treads" and the rubber heats up to soften for good grip during braking and turns. This tire has been sold in the United States as the Advan ENV-R1 racing tire for sports car races, but is not used conventionally on American roads.
According to the story, Goodyear has a unique approach to the problem. The company focuses on the chemical elements of the rubber. One compound called isoprene is increasingly unavailable as a raw material byproduct of petroleum refining. Goodyear has teamed up with biotechnology companies to figure out how to make plants produce isoprene. One company, Genecor, has developed a chemical called BioIsoprene for use in the tires. Goodyear anticipates a road testing for the BioIsoprene tires in mid-2011.
Finally, the article discusses research efforts at Oregon State University, where scientists are building plant-based fillers to be used in tires. Silica, typically used in tires, is "costly, sophisticated" and "requires a lot of energy to produce," so the researchers are trying to find an alternative that still has the same high performance. The new compound would also help limit tire weight, which further increases fuel economy for the car.
The piece concludes with a call for drivers to recycle their tires while we wait for more eco-friendly alternatives to hit the consumer market. Increasingly, manufacturers are able to reuse the recycled rubber to create new tires.