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With the success of computer modeling, Nakamura began

using the technology to address the challenges of producing a sustainable product. His dream was to create a tire made en- tirely of non-petroleum material to remove reliance on fossil fuels such as oil and coal. This would require a return to using natural rubber derived from trees. The challenge was how to solve natural rubber’s Catch-22:

its smooth, long fibers reduce a tire’s rolling resistance, result- ing in better gas mileage but also a weaker grip on the road. Nakamura’s team resolved this issue by chemically mod-

ifying the natural rubber with Epoxy resin (producing ep- oxydized natural rubber, or ENR). They further reduced the petroleum content by using non-petroleum carbon black filler and vegetable oils (in place of its petroleum equivalent), reinforcing the compounds with plant fibers. The result was a 97-percent renewable resource tire with good grip perfor- mance. Released as the Enasave tire in March 2008, it boasts a 30-percent reduction in rolling resistance and up to a 3-per- cent improvement in fuel economy. This significantly reduces a tire’s carbon footprint, as roll-

ing resistance—which causes higher fuel consumption—rep- resents a tire’s biggest environmental impact, according to a life-cycle assessment by European tire and rubber manufac- turers. “The biggest challenge of this century for transporta- tion professionals is to develop ways to make our transporta- tion systems sustainable,” says researcher Elizabeth Deakin of UC Berkeley who specializes in the environmental impacts of transportation. “Aki Nakamura’s tire design shows how cre- ative thinking and strong engineering skills can combine to advance the state of the art and improve the lives of millions of transport users.” Nakamura credits his HMC advisor for helping him make

the connection between science and daily life by encouraging him to explore piano and literature. “Liberal arts give you a notion of people’s life, society and history,” he says. “In later years, my decision making was always not what comes of this project, but how it is related to people’s life and in what way. Life first, engineering later.” Now retired, Nakamura’s legacy will be Sumitomo’s intro- duction of a 100-percent petroleum-free tire by 2013.

Koren Wetmore is an award-winning journalist specializing in health, environment, science and technology.

Aki Nakamura ’66 has worked on returning the tire to its sustainable beginnings.

Synthetic Tire’s Carbon Footprint

With one glance at the carbon footprint of a standard, synthetic tire, you can appreciate the value of Nakamura’s work toward a renewable resource tire:

• More than a half-million barrels of crude oil are used daily to make feedstock for making plastics, asphalt and tires.

• A projected 282 million tires will be manufactured this year.

• It takes about seven gallons of oil to produce a standard tire (five to produce the chemical feedstock to make synthetic rubber and two to provide energy for the manufacturing process).

• The average tire contains 60 percent synthetic rubber.

• The transportation industry accounts for about one-third of the nation’s greenhouse gas emissions.

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