Vertical Farming

In a crowded world, high-tech hanging gardens offer a way to save land, water ... and the climate

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An experimental farm in El Paso, Texas, reduces water and fertilizer waste for crops.

Dickson Despommier became the guru of vertical farming because his students were bummed out. A professor of environmental health at Columbia University in New York City, Despommier teaches about parasitism, environmental disruption and other assorted happy topics. Eventually his students complained; they wanted to work on something optimistic. So the class began studying the idea of rooftop gardening for cities. They quickly discarded that approach--too small-scale--in favor of something more ambitious: a 30-story urban farm with a greenhouse on every floor. "I think vertical farming is an idea that can work in a big way," says Despommier. (See pictures of urban farming.)

Why would we want to build skyscrapers filled with lettuce when we've been farming on the ground for 10,000 years? Because as the world's population grows--from 6.8 billion now to as much as 9 billion by 2050--we could run out of productive soil and water. Most of the population growth will occur in cities that can't easily feed themselves. Add the fact that modern agriculture and everything associated with it--deforestation, chemical-laden fertilizers and carbon-emitting transportation--is a significant contributor to climate change, and suddenly vertical farming doesn't seem so magic beanstalk in the sky.

"Vertical farming could allow food to be grown locally and sustainably," says Glen Kertz, CEO of Valcent, a tech company based in El Paso, Texas, that's trying out the process. His firm uses hydroponic greenhouse methods to grow upward rather than out. The result saves space--vital in urban areas--and allows farmers to irrigate and fertilize with far less waste.

At Valcent's El Paso lab, potted crops grow in rows on clear vertical panels that rotate on a conveyor belt. Moving them gives the plants the precise amount of light and nutrients needed, an optimization that Kertz says lets him grow 15 times as much lettuce per acre as on a normal farm, using 5% of the water that conventional agriculture does. The company aims to finish a commercial-scale facility by early 2009.

Despommier's plans are even grander. He has drawn up models for a 30-story, city-block-size vertical farm that would have transparent walls to maximize sunlight and would produce enough food for 50,000 people. "With about 160 of these buildings, you could feed all of New York," he says. His idea has intrigued architects, but Despommier concedes that it would cost hundreds of millions to build a full-scale skyscraper farm. That's the main drawback: construction and energy costs would probably make vertically raised food more costly than traditional crops. At least for now.

See pictures of the world's harvests.

See pictures of Nebraska farms.