Sound and Fury

Ok, this locavore thing is getting out of hand. Really. It is.

You do not need to build skyscrapers with farms in them, so city-dwellers can have extremely local produce, and play farmer. It's dumb. And it will most certainly not save energy.

If you live in the city, and want to grow produce, get a window box.

Farming (of any sort) has two essential inputs: sunlight and water. In a high-rise, you'd have to pump water (at a cost of around 1.5 J/Lm), and you have to use artificial lighting (at an output efficiency of around 12%, for florescent). On a normal farm, the light is free, and the pumping costs low or non-existent.

Truck transportation is mind-bogglingly energy efficient. Newer semis get 6-10 MPG towing tens of thousands of pounds. And trucks are less efficient than trains or ships. It is entirely possible that driving a Prius to the grocery store and back consumes more energy (on a per pound of cargo basis) than the rest of the transportation chain combined, even for foreign-grown goods. It is certainly worse on a per pound-mile basis.