Here's a little puzzle for you. Consider this Disney-esque depiction of a "vertical farm".
Gee, willikers - is this a neato idea! Like most agritopian "solutions" it recycles, self-energizes, and generally produces more from far less. You don't often see stuff like this outside the pages of Popular Science.
I can't believe this guy even got to page two on his spreadsheet without noticing his energy problem. How much sunlight falls on one tower? Compare with say 80 acres of corn, which has the one of the highest energy capture capabilities of any crop. The crops 3 feet away from the window on say, level 4 won't get enough energy to srpout a mushroom, let alone vegetables.
Imagine a cluster of 30-story towers on Governors Island or in Hudson Yards producing fruit, vegetables, and grains while also generating clean energy and purifying wastewater. Roughly 150 such buildings, Despommier estimates, could feed the entire city of New York for a year. Using current green building systems, a vertical farm could be self-sustaining and even produce a net output of clean water and energy. [More]
We are in the solar energy business in agriculture, and it takes millions of acres and carefully bred plants to harvest as much of it as we do. The world needs millions of acres because the sunlight intensity isn't that high - if it was we'd all be medium rare by now.
Still, this perpetual farming machine almost makes you forget that.