What do you mean? The fuel itself should be carbon neutral, even if it requires extra energy to create. I don't see any reason you couldn't make carbon neutral bio fuel, although I'd net on syngas instead.
Growing food and converting it to fuel is not carbon neutral. Farming is very resource intensive at the scales needed. In fact, it is literally the same idea as carbon capture, but via biology instead of synthetic. As a result, it is entirely a bad idea.