I came across an interesting article today on Skyfarming. The article talks about building 30 story farms in metropolitan areas.
I have been bouncing an idea around in the back of my head for something similar, if not so… extensive. My idea was to use the south 5 feet of a high rise building as a farm. The noonday sun won’t really allow much deeper reach of direct sun, especially in more southern locations. Essentially you set up a vertical hydroponics greenhouse.
If you figure 1 acre of land is 43,560 square feet. A 200 foot wide, 5 foot deep swath of a 44 story building will yield over an acre of urban “land” for growing produce. According to the referenced article, an acre of hydroponic grown strawberries is equivalent to 30 acres of traditionally grown strawberries. Other similar sized crops would be able to be grown as densely as well. Or, another view of it, these urban vertical greenhouses has potential to grow as much food (actually more) per acre of land as their rural, traditional farmland, even including the surface streets, and shorter buildings that are blocked from the sun by the towers.
Only a percentage of the building would relinquished for growing crops. The southern 5 feet would be walled off by glass walls to keep troublemakers out of the greenhouse. If the high rise was a condo or an apartment building, the residents could have access to their own little gardens in a section of the greenhouse on their floor, or they could “rent” it to the building farm coop. Local restaurants found in the first floors of these buildings would be able to have fresh, locally grown produce (within a few hundred lateral feet if not immediately “upstairs”) available to them. The low transportation costs and high yields would address the high cost per square foot value of the floorspace. (Does anybody have any numbers for this? If managed as a aquaponics vegetable and fish farm, growing lettuce just on the floor would yield in excess of 24heads/case * 45 cases per week * 52 weeks per year = 56,160 heads of lettuce and 900lbs/6 weeks * 52 weeks = 7,800 lbs of fresh fish a year. This is not even close to utilizing the space efficiently – just a rough estimate that you would probably need to produce about 10X this to make it cost effective at market prices. )
The buildings would reap other benefits beyond a regular food and income source from the rent of greenhouse space, or the direct sale of produce and flowers (depending on how the building owner did it). The large quantities of growing plants would be an active air filter, helping maintain a healthier air supply, and reducing heating/cooling costs because of the reduced need to ventilate the building. The hydroponics water could provide a lot of thermal mass and a ready distribution method for heating/cooling during the day by heating or chilling the water at night when the energy costs are lower. I am leery about gray-watering foodstuff plants, but I have no qualms about ornamental plants such as flowers. Office buildings would have a bit of the outdoors pulled inside, providing a more relaxing environment.
Maybe I would finally be able to buy a decent tomato in the city!
We have all read stories about the Hanging Gardens of Babylon, but how cool would it be to see the High Rise Gardens of Boston?