High atop Building no. 3 in Brooklyn's Navy Yard, a waterfront industrial park looking out on Manhattan, an organization called Brooklyn Grange built a 65,000 square foot farm. The Grange claims it's the largest rooftop farm in the world, and, in the time-lapse video above, Christopher St. John watched it progressed through the growing season.
Rooftop farms like this one do a number of jobs: they help keep buildings cool in summer and warm in winter, they help prevent flooding, and they provide a local source of fresh food. The big question is what role rooftop farms and other forms of urban agriculture can have in feeding cities of the future. Are urban gardens little more than fun projects, or are they a key to a sustainable city?
Brooklyn Grange has another large rooftop farm, on a roof in Long Island City, and has sold 40,000 pounds of rooftop-grown produce, says Pop Up City. This sounds like a lot. According to a 2010 report to the Mayor's office, though, New York City runs through around 28.6 million tons of food per year, meaning that for all Brooklyn Grange is doing, it's still only producing 0.00007% of New York's food.
But, according to Michael Sorkin, an architect, writing in Aeon, New York City really could become fully self-reliant one day. Working with a simulation of New York City as a walled garden, cut off from the rest of the agricultural system, he says, “We discovered that it is in fact technically feasible to produce 2,500 nutritious calories a day for everyone in the city.”
At one level, the required infrastructure is not entirely outlandish. It would depend on the widespread use of vertical farming, building over existing infrastructure – railways, highways, factories, etc – and the densification of some parts of the city currently built at suburban scale.
The problem, as always, is scale. Growing food on every square inch of New York is certainly possible, technically, but whether that makes sense isn't so clear.
The cost of making a self-sustaining New York, says Sorkin:
...would be prodigious and many of the implications highly vexed. For example, the energy required to light, heat, and build all of this is, we’ve calculated, approximately equivalent to the output of 25 nuclear power plants, an eventuality that is, to put it mildly, somewhat at odds with our larger intentions....
New York owns a watershed upstate and a remarkable set of aqueducts to bring what it captures to the city. It makes little sense to grow most grains in the city when they are produced and transported so efficiently from the Midwest.
So will rooftop farms ever be able to fully sustain the city? Maybe. But if the goal is to bring the city into balance with the larger ecosystem, trying to disconnect the city from the global economy may not be worth the cost.