Grain price rise and biofuel

I post this question in GD rather than GQ because I think the answer is debatable.

The recent escalation in the price of various grains is being discussed a lot. How much of that price rise can be attributed each of these potential causes?

  1. Biofuel mandates? Farmers are incentivized to grow for biofuel rather than food.

  2. The rise in fuel prices needed to produce the grains? It costs more to plant, fertilize, and harvest the grain due to higher overall fuel prices.

  3. Simply the loss in value of the dollar? Oil is more expensive, partially because of the dollar itself. Does this also affect grain prices in the same way?

  4. Something else that I haven’t thought of?

1 and 2 yes. 3 no - more of an issue in other markets that pay in other than dollars. 4 yes. Including a more affluent China eating more and especially eating more meat (which costs more grain per satisfied belly than grain does) and a drought in much of farmland Australia that has caused an acute rice shortage in the East which gets much of its rice from Australia in typical times. Add in that subsidized exports in the West have depressed capacity in the Third world and that wars and poor policies (see Zimbabwe) have interrupted planting and harvest cycles with regularity too. Then fear causing certain governments to halt exports even though they do not have an acute shortage themselves.

Which one most? Danged if I know. Think of it more as a perfect storm.