Does Urban Farming Make Sense?

Matthew Yglesias just posted a thought referring to a recent NY Magazine article about skyfarming:

Should we build agricultural skyscrapers in-or-near our major cities? It’s certainly a cool idea. I think I’m going to put the notion that this is actually environmentally sound and feasible in my “too good to check” file. More plausibly, green roofs really are an environmentally sound idea, though not something with a good prospect for replacing farms.

Check out the article, it’s very cool. Here’s my take:

I think this would be really cool, but I can’t imagine this being economically feasible, except under extreme circumstances.

1. To locate this in a dense city would mean it would compete for land with the most expensive office and residential properties, where developers pay huge land prices to build in those locations. They build there because the most productive companies and individuals desire to locate there and can pay for it. The competition from farms, of all things, would drive prices for office and residential even higher.
Perhaps, it might make sense to locate on less desirable urban land such as near highways or industry.

2. Construction costs of building vertical are enormous. Especially compared to the construction cost of traditional farms: nearly 0.

3. Labor costs: city labor is much more expensive than rural labor. Perhaps the skyfarm will be fully automated, but you’ll need engineers on site and other staff a typical farm does not require.

4. Traditionally, farms locate on land that is much less productive than agglomerative cities, which is why land is cheaper and farming can become profitable. Add in extraordinary construction costs, and it makes little economic sense. I can’t imagine farms competing with urban offices in productivity or profit per square foot.

5. The skyfarm probably isn’t so good for the environment. The construction materials used to build the structure must be transported from somewhere and required significant energy and resources to produce. This compared to a traditional farm, which requires little construction. The skyfarm would displace other productive uses such as offices, causing them to locate in less ideal places, and encouraging sprawl and transportation inefficiencies.
One should be skeptical of any “environmental” solution that costs significantly more than conventional alternatives, because there are often less obvious environmental costs reflected in the production costs of a higher-priced good.

The price of food would have to be really tremendous to justify the rent and production costs of food in this facility. I suppose, if it is good at generating energy, and cleaning water, that would offset some of the costs.

Or, the costs of transporting goods would have to astronomically higher than today, making it reasonable to have food grown nearby. However, if that were the case, land prices would be even higher in big cities and transporting construction materials would be more expensive.

Nonetheless, farming, or at least recreational green roofs could be effectively done in underutilized space, such as rooftops or building atriums. However, a green roof requires more structural material and construction than a conventional roof. But, where greenspace is scarce, it is often worth the cost.

And here’s a slightly more feasible urban farm:

ULI’s The Ground Floor – The Ultimate Green Building
NY Mag – Blue Sky on Canal Street

From Austin Contrarian – Very, very expensive farmland (updated):

If you assume that an acre of hydroponic “land” can support 10 people per year (a generous estimate), then 8,000 acres could support 80,000 people per year — or 1% of New York City’s population.

8,000 acres is roughly 348 million square feet, which, coincidentally, is almost exactly the size of Manhattan’s entire inventory of office space. So to meet just 1% of NYC’s annual food needs, you would have to find space in NYC to duplicate one of the planet’s great concentrations of skyscrapers.