Are Vertical Farms the Answer After All?

High-Tech Greenhouses See 20-Fold Increase in Yields
Adam Stein of Terrapass was famously skeptical about vertical farms, describing them as "pie in the sky". So I was surprised to read one of his latest blog posts, in which he links to an LA Times article about high-tech California greenhouses that are employing vertical farming techniques, and boosting crop yields per acre by a factor of 20. Could it be that Adam was wrong about vertical farming? The original article from the LA Times pays a visit to a Camarillo-area greenhouse run by Casey Houweling. The facility is designed to recycle rainwater, generate power, eliminate herbicides and cut pesticide and fertilizer use dramatically:

On a recent afternoon, he was eager to show visitors clusters of plump, sweet tomatoes hanging overhead from vines that reach high into the rafters. This arrangement allows the farm's 450 permanent employees to climb ladders to pick the fruit instead of stooping. The plants, which are fed individually through tubing that looks like intravenous hospital equipment, produce 20 times more fruit per acre than in conventional field production.
Virtually nothing is wasted in this ecosystem. Workers have dug a four-acre pond to store rainwater and runoff. This water, along with condensation, is collected, filtered and recirculated back to each of the 20-acre greenhouses. That has cut water use to less than one-fifth of that required in conventional field cultivation. Fertilizer use has been reduced by half. There are no herbicides and almost no pesticides, and there is no dust.
Five-acres of photovoltaic solar cells supply much of the electricity to run pumps and climate controls. Thermal systems collect solar heat and warehouse refrigeration exhaust to warm the greenhouses on cool evenings. Together, the two systems generate 2.1 megawatts of electricity, enough to power 1,500 homes. "We believe this is the first greenhouse in the world that is energy neutral," Houweling said.

So Adam Stein must be eating his words about vertical farming? Not so fast. Adam argues (pretty convincingly) that technological farming advances are great, but it still makes little sense to use up prime (expensive) urban real estate to grow food rather than house people:

"Does this mean I was wrong to knock vertical farms? The answer is (surprise!) no. The article makes clear that the success of these high-tech farms, as with all farms, is exquisitely sensitive to input costs and food prices. It makes most sense to site them in California, because the sunny, temperate climate means more growing days and less need to spend energy on heating and cooling. And nothing about the new greenhouses addresses the sunlight issue that troubles multi-story designs.
In other words, technological advances may make future farms vastly more efficient, but these improvements won’t erase the comparative advantages of certain growing regions. This isn’t a problem; rather, it’s a good thing. Our farms will get better at producing food, our cities will get better at housing and moving people, and our environment will benefit.

Anyone care to mount a counter argument?