excerpt from Special Report: Cars Made of Plants?
http://www.edmunds.com/advice/fuelec...1/article.html

But Do They Perform?
Are automakers sacrificing anything to use biobased materials? As it turns out, biobased car parts typically work better than the parts they replace. For instance, Honda's engineering team found that the wood fiber-reinforced floor provided better dimensional stability than the other, more traditional materials being considered.

Likewise, Goodyear has found that its corn-infused tires have lower rolling resistance than traditional tires, so they provide better fuel economy. And DaimlerChrysler notes that plant fibers' ability to absorb large amounts of humidity makes them perfect for use in seat cushions, where they can increase occupant comfort.

According to BMW, it's possible to manufacture biobased composites that are as much as 40-percent lighter than equivalent injection-molded plastic parts. That's because natural fibers have high-tensile strength, durability and rigidity, plus they're easy to process and lighter in weight than glass fibers, all of which makes them excellent for reinforcing composites.

Using plant fibers in composites provides additional advantages in terms of product design flexibility, noise absorption, insulation, impact-resistance and even a reduced tendency for parts to splinter in a crash. Plus, weight reduction translates directly into better gas mileage.