According to Friends of the Earth, even when no harmful chemicals have been used to produce a certain type of crop, intensive mono-agriculture (growing a single crop) leads to the destruction of forests, savannah and wildlife. Mono-agriculture also makes land prices soar and does not improve production methods. The environmental organisation also stated that most of the crops that are used for biofuels are currently under the control of big corporations that just want to sell more of certain agriculture products, so they keep the demand high. In short, FotE says, sustainable means more than some might admit.
[Source: Friends of the Earth]