There has been a recent spurt of media about "vertical farming". I have dismissed this idea as fundamentally flawed for one simple reason: energy constraints.
Amazingly, even fairly detailed plans gloss over the solar energy input problem.
For building constraints, we assumed we would be working with a space approximately the size of a turn of the century tenement building typical in New York City: six floors tall with a ceiling height of 9 feet and an average of 1500 square feet per floor. Given this size, we expect to grow two rows of crops per floor on the top five floors of the building thereby doubling our yield capacity. Calculations for crop yield are based on 3000 square feet. Based on the calculated square footage, our expected yield is (see Appendix 2 for the conversion to metric units, the editor):
The growing media chosen for the crops is perlite. Perlite is a processed mineral that allows a constant concentration of water and nutrients (47). If maintained properly, perlite can withstand many years of use without degrading (48). Two concerns with using perlite are its poor pH buffering capacity and propensity to encourage algal growth (49). However, with proper inspection and maintenance of the growing equipment, we will avoid any of these potential drawbacks. Figure 1 details the nutrients as well as certain other environmental conditions required for proper growth of each crop. All nutrients will be drawn from the composting and black water, both detailed elsewhere in the paper. We will not need to rely on outside sources of fertilizer. This self-reliant closed system serves to greatly reduce the amount of pollution related to transportation, fertilizer, pesticide and herbicide production. Manual pollination performed by employees will be used for those plants requiring it. [More]
- Lettuce: 688 lb.’s/100/square feet, 20,640 lbs/3000 square feet (42)
- Cucumbers: 932 lb.’s/100 square feet, 27,960 lbs/3000 square feet (43)
- Tomatoes: 835 lb.’s/100 square feet, 25,050 lbs/3000 square feet (44)
- Sweet potatoes: 1,200 lbs/100 square feet, 36, 000/3000 square feet (45)
- Strawberries: 333 lbs/100 square feet, 10,004 lbs/3000 square feet (46)
Tell me again how, say, the 3rd floor down produces squat away from the windows. Mostly these proposals gush over water reclamation systems and "closed loops" efficiencies. (We do love the idea of nothing going to waste!)
Consider just one design:
Basically stated these buildings won't get enough sunlight to power the growth of floors of plants. Think about it - other than those crops at the wall and on the top floor, the every thing else is in shadow. And the walls are in shadow at least half the time, right? While they may steal some light from neighboring buildings who are now in shadow more, how much of a gain is that? Their share of available sunlight is close to the same as the building footprint.
This also assumes sombody doesn't build an eqully tall building next door as well.
So are they using artificial light? That sure screws up the economics. [Ask pot growers] This whole idea seems terrifically illogical, albeit futuristically attractive.
Simply put, there is a reason we cover mucho flat acres with crops. It's how you harvest the dilute energy from the sun, which is essentially the real business of agriculture. It's also why the corn rows next to the woods are about 50% yield even in good years.
Surely somebody has pondered this problem. But just in case, it will be interesting to watch one of these follies get built. Consider this assertion in Scientific American, no less:
A one-square-block farm 30 stories high could yield as much food as 2,400 outdoor acres, with less subsequent spoilage. [More]OK, why not build it umpteen miles high and eliminate all the farmland?