TED fellow Viraj Puri talks about his Brooklyn rooftop farming startup. Gotham Greens has ~1500 square meters of hydroponic greenhouses producing herbs and salad greens in a very controlled environment… somewhere between a farm and a manufacturing facility. The system is solar powered, and can operate all year long. They currently produce ~100 tons of food a year, and they believe the business is viable at least in the urban foodie context. I was happy to see Puri readily (repeatedly) admitting (or even pointing out) that the system cannot scale up sufficiently to provide a large proportion of the city’s overall food requirements. This is in stark contrast to the idea of Vertical Farming, which is clearly bunkum — once you’ve covered the roofs with greens, there’s no more farming to be done unless you pipe in light somehow, which is much less efficient than simply farming where the light is naturally.
Just out of curiosity… I wonder how much food could be produced in Brooklyn at full capacity? And roughly how much does the city eat? The land area of the borough is 183 km^2 and it has 2,500,000 residents, or roughly 75 m^2 per person. Their production of 100 tons/1500 m^2 is roughly 66 kg/m^2 per year. So if the entire area of Brooklyn were producing like this greenhouse, you’d get nearly 5000 kg of food per person per year. The average American consumes about 1000 kg of food per year, so if you were able to use 20% of the borough’s area, you’d be close to meeting demand… at least by mass. Gotham’s 59kW solar array probably takes up ~590 m^2 (100 W/m^2 is typical of solar cell power production) and only provides part of the operation’s power. Probably there’s other infrastructure too that’s not actively producing food, so say they’ve got about half their total area dedicated to actual plants… then you’d need to get up to 40% of the land area being utilized to get 1000 kg of greens per resident per year.  However, most of the 1000 kg that we actually eat is a lot more energy dense than lettuce. I wonder how many calories per m^2 one can get out of these setups, and what the most productive crops would be? Honestly I’m surprised at how large the potential production is. I wonder what the actually available rooftop area is?