Well, I'm not trying to avoid your question, but it depends on the boundary conditions and how many opportunities you are trying to achieve in that vertical farm. I know of a vertical farm in the Netherlands with a dairy operation, aquaculture and hydroponics. There are about seven commodities being produced in that farm.
First of all, depending on what you put in your vertical farm, the energy will vary. It will dramatically decrease the land footprint. We can draw from the example of the greenhouse industry in southern Ontario right now what this is capable of doing, because tomato production within a greenhouse can be two to four times higher in yield than it is off the landscape. I want you to check me on that figure, because I'm not a tomato producer—I'm a happy consumer of ketchup.
As we move forward in the innovations we're looking at, if you were to put a vertical farm within the city, I think that would be a wonderful use of old school gymnasiums or whatever; if there's a school pool there, why isn't it filled with tilapia? You can shorten the distance for local food. I don't know what “local food” is, because people are going to be darned hungry if they rely on something being grown within 100 miles of Toronto; I don't think you've found anything yet that resembles soil, to get away from the pavement. The sarcasm there is intended.
The reality is that still again you have to define your system a little bit more tightly to be able to properly answer that question. The landscape right now is continuing to bring us more and more because the innovations are being used on that landscape to maximize their potential.