By BINA VENKATARAMAN

What if “eating local” in Shanghai or New York meant getting your fresh produce from five blocks away- And what if skyscrapers grew off the grid, as verdant, self-sustaining towers where city dwellers cultivated their own food?
Dickson Despommier, a professor of public health at Columbia University in New York, hopes to make these visions a reality. Dr. Despommier’s pet project is the “vertical farm,” a concept he created in 1999 with graduate students in his class on medical ecology, the study of how the environment and human health interact.
The idea, which has captured the imagination of several architects in the United States and Europe in the past several years, just caught the eye of another big city dreamer: Scott M. Stringer, the Manhattan borough president.
When Mr. Stringer heard about the concept in June, he said he pictured a “food farm” addition to the New York City skyline. “I think we can really do this,” he added. “We could get the funding.”
Dr. Despommier estimates that it would cost $20 million to $30 million to make a prototype of a vertical farm, but hundreds of millions to build one of the 30-story towers that he suggests could feed 50,000 people. “I’m viewed as kind of an outlier because it’s kind of a crazy idea,” Dr. Despommier, 68, said .
He says his ideas are supported by hydroponic vegetable research done by the United States space agency and are made feasible by the potential to use sun, wind and wastewater as energy sources.
Several observers have said Dr. Despommier’s dreams are unrealistic.
“Why does it have to be 30 stories? said Jerry Kaufman, professor emeritus of planning at the University of Wisconsin, Madison. “Why can’t it be six stories- There’s some exciting potential in the concept, but I think he overstates what can be done.”
Armando Carbonell, chairman of the department of planning and urban form at the Lincoln Institute of Land Policy in Cambridge, Massachusetts, called the idea “very provocative.” But it requires a rigorous economic analysis, he added. Dr. Despommier agrees that more research is needed, and calls the energy calculations his students made for the farms, which would rely solely on alternative energy, “a little bit too optimistic.”
Augustin Rosenstiehl, a French architect who worked with Dr. Des pommier to design a template “living tower,” said he thought that any vertical farm proposal needed to be adapted to a specific place. Mr. Rosenstiehl, principal architect for Atelier SOA in Paris, said: “We cannot do a project without knowing where and why and what we are going to cultivate. For example, in Paris, if you grow some wheat, it’s stupid because we have big fields all around the city and lots of wheat and it’s good wheat. There’s no reason to build towers that are very expensive.”
A smaller-scale design of a vertical farm for Seattle won a regional green building contest in 2007 and has piqued the interest of officials in Portland, Oregon. The building, a Center for Urban Agriculture designed by architects at Mithun, would supply about a third of the food needed for the 400 people who would live there.
For Dr. Des pommier, the high-rise version is on the horizon. “It’s very idealistic and ivory tower and all of that,” he said. “But there’s a real desire to make this happen.”