Chemical fertilizers (made from natural gas) and chemical pesticides are not sustainable, and corn is one of the least efficient crops in terms of energy input; so corn ethanol is not a viable biofuel. Obviously, tearing down rainforest is a stupid thing to do, for any purpose.
A crop like jatropha makes a lot more sense, and might be sustainable. It is a perennial, grows in drought conditions on marginal land, as I understand it. It has a lot of oil in it's seeds/fruit and it makes very good biodiesel.
Jatropha - Wikipedia, the free encyclopedia
All energy on Earth came originally from the sun or from the gravity generated by the Earth and/or the moon. Why wouldn't it be these be the best sources for energy?
Solar heat and solar PV, wind power, wave power, tidal power, geothermal power, small scale hydro -- none of these burn any fuel or consume anything to produce power. There is no waste produced when they are generating electricity. Their power source will keep going and going and going...
What's not to like?