Atypical farm burns vast quantities of fossil fuels to plow fields, sow seeds, reap harvests and truck products many miles to population centers. It spreads heaps of petroleum-based fertilizers, which then run off into streams and watersheds. It also consumes rivers of freshwater and casts pesticides across the countryside. Raising chickens and pigs further insults the earth with unhygienic filth.
Why not grow grains, vegetables and fruits right where the expanding crowds of consumers are: in the middle of a city, inside a tall glass building? Poultry and pork could be reared there, too. A vertical farm would drastically reduce the fossil-fuel use and emissions associated with farm machinery and trucking, as well as the spread of fertilizer and its runoff. Crops could grow and be harvested year-round instead of at the end of one season, multiplying annual yield by at least four times. Urban agriculture could also convert municipal wastewater into irrigation water, reducing a city’s refuse problem. And consumers would get the freshest food possible, without pesticides.
A fanciful notion only a few years ago, vertical farming has captured the attention of large developers that are planning more sustainable cities, such as the multinational firm Arup, and municipalities that are looking to reduce environmental damage and the cost of treating wastewater. Although growing crops in downtown skyscrapers may seem strange, Dickson Despommier of Columbia University, who has championed the movement, says the practice makes perfect sense. “When it’s 98 degrees and 80 percent humidity outside, we humans sit inside a controlled environment that is 72 degrees and 25 percent humidity,” he says. “We’ve done that for our homes and offices. Why can’t we do that for our crops? Well, we can.”
Proponents also say we must. If, as demographers project, the world’s population rises from six billion to nine billion by 2050—almost entirely through a net addition to urban populations—the planet will need to cultivate a billion more hectares of arable land, roughly the area of Brazil. Researchers say that much arable land simply doesn’t exist.
The science for indoor farming does exist. Agronomists have developed crops that thrive in lightweight, engineered soils such as vermiculite or in water (hydroponics). NASA has devised crops that grow by dangling in air infused with a mist of water vapor and nutrients (aeroponics). Large greenhouses in several countries, notably the Netherlands, are producing substantial yields using these techniques. According to Despommier, a 30-story farm that covered a city block could feed 50,000 people year-round.
Skeptics worry that indoor crops would have to be genetically modified to thrive, but Despommier says such alteration is unnecessary: “None of these crops has to be modified further for life indoors. In fact, they’ll do much better because we can match their growth characteristics with temperature and humidity conditions and nutrition profiles.”
Engineering that environment itself is the greater challenge. Providing sufficient light and water is relatively easy. What’s harder is controlling the indoor flow of air and nutrients, efficiently recycling water and devising high-tech incinerators that burn plant waste to produce energy that augments wind and solar power.
Operating costs are an issue, of course, including winter heating and harvesting. But the fertilizer and fuel consumed for traditional farming is expensive, too; witness the run-up in food prices this year. Governments also pay out billions of dollars annually to rescue farmers who lose crops to drought and floods such as those that ravaged the Midwest this past June.
Although real estate in cities would seem too pricey for farming, Despommier’s graduate students surveyed New York City and found many abandoned buildings and lots where high-rise farms could sprout. “And they don’t all have to be big towers,” Despommier allows. “You can do this on the rooftops of hospitals and schools,” which would use the food in their own commissaries. “You can do this along the periphery but still within city limits. You can do this on open stretches of air force bases and airports and city islands.”