In the next 50 years, the U.N. estimates the world’s population will reach roughly nine billion people, and the vast majority will live in cities. Feeding those hungry mouths, experts say, will require clearing an additional ten billion hectares for farming—that’s an area roughly the size of Brazil. But Dickson Despommier, a microbiologist at Columbia University, doesn’t believe that chopping down the world’s forests to make new farmland is the answer to easing potential food shortages. Instead, he wants to bring farming to the places where most consumers and supermarkets are—namely, cities. Forget community gardens and the occasional greenhouse; Despommier and a team of his students propose farming in skyscrapers, or “vertical farms.” They envision 30-story buildings that each take up a city block and grow enough food for 50,000 people per year.

“It’s not just a way of generating food,” says Despommier. “It’s a way of dealing with municipal waste, recycling water, and using methane digestion to help a city be sustainable.” According to his scheme, both animal and plant life could thrive indoors. Fish such as tilapia, trout, and striped bass would live in the pond on the ground floor, while fruits and vegetables would be grown hydroponically, without the use of soil, on upper floors. Wastewater from the fish tanks would be transported to the basement where, along with drain water from showers and sinks, it would be treated and then used to fill the fishponds and hydroponic tanks. Water containing human wastes and other organic material would pass through a methane reactor to create energy to power the building. With no need for pesticides or food transportation, and the ability to produce multiple crops in a season (six corn harvests, for example, instead of one), the vertical farm sounds like an eco-cornucopia.

Although this smacks of science fiction, industries operating on a similar principle are already up and running. In 2001, the Dutch agriculture minister supported building a vertical farm in Rotterdam called Deltapark, in response to flooding farmland, livestock diseases such as swine fever, and growing agricultural pollution. Though the park hasn’t been built, the idea of linking several industries together to reduce the environmental burden of agriculture has become increasingly popular, says Jan Broeze, the Wageningen University scientist who dreamed up Deltapark. “If you cluster various activities, like greenhouses, fish farming, and manure processing, then you create a sufficient scale for more sustainable food production,” says Broeze, who is working with a group of farmers in Holland to link a chicken farm, a manure processing system, and greenhouses. “The idea is to use wastes from one industry to sustain another.”

In the U.S., however, the idea has generated interest but not capital. “The problem is that nobody wants to be first,” says Despommier. “I think this will arise when someone realizes that they can make a lot of money.” He compares the vertical farm to the hybrid car, which “now everybody is producing. They aren’t doing it for the sake of the environment; they’re doing it to make money.”

Vertical farms will likely become more economically viable in the coming years, according to John Ikerd, an agricultural economist at the University of Missouri-Columbia. “There will be even greater economic opportunities in the future, as the prices of industrial foods rise, markets for local and sustainably produced foods grow, and production systems for vertical farms become more efficient through research and practical experience,” he says.