The overall carbon footprint of a vehicle is more than 90 percent composed of the fuel used to move it around, but manufacturing plays a role too. Many automakers are quietly working to include more renewable materials into a product that's largely made of metal, plastic, and glass.

The latest example comes from Ford, which reinforces plastic storage bins and door panels with wheat straw--made from the wheat-plant biomass you see waving in the air when you drive past the Midwest's prevalent wheat fields.

The research leading to the new material was jointly funded by the Canadian government's BioCar Initiative along with four universities, plus their industrial partners. The University of Waterloo, in Kitchener, Ontario, worked with wheat straw because it's in the midst of a wheat farming area.

2010 Ford Flex

2010 Ford Flex

The wheat straw has similar properties to such other agricultural materials as wood fiber, hemp fiber, coconut coir (husks), and purified cellulose fiber. Experiments using each of them to reinforce injection-molded plastic parts are now underway across North America.

For compression molding, where the renewable materials may one day displace glass-fiber or mineral reinforcements, candidates include both flax and the family of prairie grasses that includes the delightfully named Big Bluestem and Indian Grass plants.

The hope is that not only will the overall carbon footprint of vehicle manufacturing be reduced, but the organic fibers may weight less than today's reinforcements--reducing overall vehicle weight and contributing to improved fuel efficiency.

Ford has other green materials initiatives underway. One makes fender baffles for its new 2011 Explorer SUV out of leftover steel from pickup-truck body sides stampings. Another is development of soy-based rubber for use in a variety of vehicle parts.

And beyond Ford, one of our favorites is tires made in part from orange oil. In fact, everything from old carpet to blue jeans may end up your new car these days, spurred by carbon reduction, recycling, and in some cases, cheaper costs.

Still, it's important to keep these efforts in perspective. Every little bit counts, but increasing fuel efficiency can have a much bigger impact on a car's lifetime carbon footprint than incremental trimming in the manufacturing process.

According to a study done in 2000 at the Massachusetts Institute of Technology, On the Road in 2020: A Lifecycle Analysis of New Automotive Technologies, 75 percent of a vehicle's total carbon footprint is due to the fuel it burns. And 19 percent more comes from manufacturing and distributing that fuel.

[Ford, Vermilion Standard]