[sustran] How much land does a car "eat" for a year?

[chuwa]

Sorry if this subject sounds funny. 

The long question is:  
How much land is need to produce enough bio-fuel for a typical car for a year?

This a a question I asked my boys to trigger them to search for an answer. I don't have the answer and I would really appreciate if anyone can point me to useful pages which may contain the answer (for primary /secondary student level).

After they found the answer, the next question will be:
If this piece of land is used to grow food (e.g. rice), how many people can it provide for a year?

With thanks,

Chu Wa