The biofuel crops are based on insight, most of energy of solar radiation is wasted in rotting of grass and weed, under releasing of methane or carbon dioxide, which are green house gases. If it's so, why to not to use this energy for human purposes? The vegetation has a positive effect into local clime and it's definitely more friendly with respect of biosphere, then the desert covered by solar cells.

The main problem is, the method of energy production depends on rich source of watter and the minerals (the nitrogen and phosphorus] must be returned into soil again - or such model will not remain feasible from long-term perspective: it will create a desert from land, not vice-versa..