Urban Farms and Locavorism
On pages 300-304, David Owen gives a compelling argument about why locavorism is actually an energy-intensive, inefficient way to produce food:
"The distance that a particular food item travels between its grower and its ultimate consumer is not a accurate measure of the amount of energy that was required to put it on the table...The California raspberries I purchase at my grocery store have a smaller carbon footprint than the local raspberries I picked recently at a farm just a couple of towns away, because the California raspberries crossed the country in a shipment containing tons of other produce and therefore represent a minute expenditure of fuel per berry, while the local raspberries were obtained by my wife and me during a thirty mile round-trip in a car whose only other cargo was ourselves" (p. 300).
Owen goes on to further develop the idea that costs other than those of transportation such as labor, fertilizers, etc. must be counted when the cost of locally-produced food is calculated. He also criticizes Dickson Despommier's idea of "vertical farming" for creating wasteful infrastructure needed to build vertical farms in the city since Owen feels Manhattan land could be used for more valuable things than farming.
Interestingly enough, Despommier was one of the speakers at the Municipal Art Society Urban Farming panel that I attended on November 4th and he discussed vertical farms (his book about them will be published next year). He advocated building the farm as a working component of the building design. For example, greenhouse gases from the farm would be used to heat the building. One building being discussed would have a cafe that used only food grown in the building's farm.
Another speaker on the panel mentioned that if all the yards in the five boroughs were used to grow food, then 750,000 people could be fed from it. Despommier talked about the enormous amount of grey water that NYC produces every day - enough, if treated (in my opinion) to water those yards while growing water-hungry vegetables. Other panelists talked about rooftop gardens but warned that the structure of the roof must be able to accommodate the weight of wet soil. While it would be pricey to retrofit roofs, it is possible for new buildings, like the one being discussed, could be designed with the idea of a roof garden. However, as Owen points out, the increased load-bearing capacities of the roof design would be an extra cost to be factored into the cost of any food that it produces.