After cars, the food system uses more fossil fuel than any other sector of the economy — 19 percent. […] modern food processing and packaging and transportation have together transformed a system that in 1940 produced 2.3 calories of food energy for every calorie of fossil-fuel energy it used into one that now takes 10 calories of fossil-fuel energy to produce a single calorie of modern supermarket food.
Insightful piece by Michael Pollan entitled “An Open Letter to the Next Farmer in Chief.” This is an excellent introduction to modern food issues in the US.