Biofuels are an unsustainable solution. They require phosphate fertiliser, but phosphate will hit peak in 30 to 40 years just like peak oil. Unlike peak oil, the only replacement for phosphate is recycled shit.
If we continue to use biofuels crops, we will not only run out in a few decades, but we will also create competition for our food sources. With a rising population and emerging India, China and Latin America, I really don't think that increasing food competition is a good idea.
The point is, the only biofuels that will work are those that:
a) don't require an outside source of phosphate (possibly algae, or perhaps just crops genetically modified to be super-efficient at extracting it from normal soil)
b) are based purely on waste products (i.e. the crops weren't created purely for biofuels)
That said, Brazil's biofuel use isn't bad. But it can't continue expanding (not least of all because of the Amazon, but also for reasons above), and the rest of the world can't afford to replicate it (again, food shortage).
It's also inefficient compared to solar, wind, hydro and geothermal. It's basically a superfluous option suitable for Brazil only because it has already invested in it.
