You are probably going to be surprised by my answer and is likely not something you'd normally expect to hear. This issue really depends on several factors. When it comes to growing crops to produce fuel, it is not really an alternative and it actually cost more to produce because you still need products derived from fossil fuel to grow it.
On the other hand, biofuel could also be derived from organic waste product as well. These fuels can be derived from dead plants and other waste products.
I'm surprised no one has pushed to convert poop into an energy source. In my opinion it's the perfect alternative in dealing with both environmental and energy issues.
The supply of poop is abundant and is produced daily and can be utilized through the existing sewage system. lol. Keeping poop out our system helps the evironment to stay cleaner while providing an excellent source of energy as poop is an organic matter that has already been broken down. It just needs to be processed and refined.
Believe it or not this can actually resolved many worldly problems with environment, energy, and food supplies because it frees up many other resources.