Biofuels is one of those issues that I'm just ish about. And now there's so much in this thread that's grabbing my attention, I don't know where to go with it.
The general idea of using food for fuel is absurd to me. I also take issue with the fact that most of the grain grown in the US is used for feeding livestock, not for feeding people. Now we're going to start putting it in cars? Ridiculous. We could feed the entire world many times over with the amount of food we grow, but it's not possible considering the way it's distributed. Furthermore, it's important to note that the corn grown for livestock feed and ethanol is NOT the same corn that we eat, at least not directly. it is the same stuff used for highly processed food additives like high fructose corn syrup. Imagine how much land, money, water, and petrochemicals we could conserve if we used only a small portion of the land that grows all that mostly useless (but highly subsidized, therefore profitable) field corn for real human food like oats, wheat, beans and vegetables. Or turned it into diverse farm operations that use more efficient methods like cover crops and rotational grazing.
There are many reasons to buy locally that have already been explained very well. I like shopping farmers' markets because the person I hand my cash to is the same one who planted, tended, and picked the tomato I'm buying. I know who grew my food, and that's important to me.
Back to carfree living. It's far more complicated than just reducing CO2. And even if we switch all personal and commercial vehicles to non-fossil fuels, we still have all the other problems that come with relying on personal autos for transportation--sprawl development, amazingly high rates of injury and death from car crashes, health epidemics like asthma and diabetes which are both caused by and exacerbated by sedentary lifestyles, urban decay from freeways that chop up and isolate neighborhoods, ... It's going to take a lot more than just finding alternative fuels. One of the huge steps we need to take is reducing our dependence on cars, not just reducing dependence on oil.