There's more that one way to green a car, and many of the most interesting technological advancements don't involve powering an internal combustion engine. Consider that much of the fabric, plastic and rubber that goes into a car's construction is derived from petroleum, and you see why alternatives are becoming increasingly attractive. Automakers have taken up corn-based plastics and soy-based seat foam, and now the latest greenery comes by way of defatted soy flour. The latter is an organic substance that's being considered as a replacement for the petroleum-based "carbon black" rubber particles that are currently specified in the vast majority of tires.
The technology has a long way to go before we could be driving on soybeans, and there are likely issues involving using a possible feedstock as a petroleum replacement (again) that will need to be worked out. Still, as pressure builds to abandon the use of petroleum in as many ways as possible, advancements are likely to become a bigger part of our day-to-day transportation needs.