Yes, there are a wide variety of bio fuels, some better than others, but...
I've always been more excited about reducing dependency on automobiles all together rather than just fueling "car nation" with vegi-fuel.
Transit, bicycles, tele-commuting and denser urban living is the way to go.
In some third world countries, food is becoming real expensive due to competition between eating and driving. Fueling vegi-cars has taken food away from the mouths of people. This is a sad consequence of vegi-driving.
Here in USA, some environmentalists have predicted the demise of our food industry as well. High oil prices means less agri-business-trucking to the supermarkets.
Do they say we should all get cars and move out to the country where we can grow our own food, rather than living in the city where we can walk to work and the supermarket?
Here in the city, food prices have risen a bit, but it's not catastrophic, not here in America at least. We can adjust as we have a lot of agri-business-trucking infrastructure for wiggle room. Rural residents are struggling more with their high gas prices, but food prices go up more modestly.
In some third world countries, the food situation is far worse. Vegi-driving in USA and other places is literally robbing corn from the mouths of people in countries where there is less wiggle room in the "agri-business-trucking" economy to absorb the price.
I'd rather eat my vegetables and then ride my bicycle home from the supermarket.