Once energy was cheap - cheap enough that the idea of growing plants for their energy seemed absurd. Obviously, plants are grown mostly for food. For thousands of years thus it has been, so shall it ever be.
But now energy is dear - dear enough that some plants in some places can be profitably grown for energy, creating biofuels. This takes space and other resources away from growing plants for food. The old conventions are being abolished. The agricultural landscape has been permanently altered.
Much to the discomfort of many. The idea of farming to feed cars is somehow deplorable compared to farming to put food on the table. But this is knee-jerk alarmism. Consider:
1. If the criterion is getting the most quantity of food out of given farmland, then even now we are not doing it. The reason? We eat animals. And animals need to be fed. Either with plant feed - which often takes away land for growing food for direct consumption - or worse, other animals, which themselves need to eat plants. And the feed conversion ratio is (aside from poultry) is much higher than 1 (reaching up to 8 in the case of ruminants). Anybody complaining about the corn we feed to hogs rather than directly to people?
Come to think of it, everytime we set up a shopping mall, a parking lot, a school, a laboratory, we are taking away land that could be used for farming. Bad for "food security". Tsk, tsk.
2. There are a lot of distortions introduced by policies. Particularly notorious are the biofuels incentives in the US, which artificially makes it profitable for some US farmers to plant for energy rather than food. Take away these incentives and we'll see a lot less of this diversion from food to fuel. Rather other options may be explored, such as growing energy crops on marginal lands. (There is some promise from crops such as sweet sorghum and Jatropha plant for such options.)
3. Food will get more expensive. Bad for consumers. But this is good for farmers. Without deeper analysis, we can't tell whether the net effect is anti-poor.
My best guess is, biofuels will play a role in the overall energy mix, but not a major one (at least within the energy sector). However within the food sector the emergence of biofuels will have long term implications for the trend in future food prices. The era of cheaper and cheaper food is over, as well.