An interesting issue in this matter is that developed world farmers are supported to produce cotton, sugar, meat etc. and the surpluses are dumped on the world market, limiting development of the others in the world.
One can also define a subsidy to the petroleum industry for the military protection they get. But this reaches probably the political boundaries of these Forums.

For the bio fuels one must not only make an economical picture, but also make energy balance calculations, for the reduced tax on agricultural fuels can make it economically viable but the energy balance can be less positive as suggested.

Can developed world farmers convert to bio fuel producing farmers in such a way they earn a proper living and make the world less dependant on fossil fuels? Can it reach a fully sustainable energy supply?

With kind regards,
Bart