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Vertical farms would grow crops hydroponically, in a water-and-nutrient solution, or perhaps aeroponically, using a mist of nutrient-laden water. ((Damian Dovarganes/Associated Press))

Is it an elegant solution to pressing problems related to the food supply, or another example of putting too much faith in technology?

That's a tough question to answer. But what is clear right now is that vertical farming is in its infancy.

The idea is to grow food inside buildings — not conventional greenhouses, but multi-storey buildings, quite likely in cities — in closed ecosystems using hydroponics rather than soil, and without the use of pesticides.

So far it has only been tried on a very small scale. Paignton Zoo in South Devon, U.K., for example, is growing produce to feed some of its animals.

But advocates of vertical farming — notably Dickson Despommier, a Columbia University professor of public health — envision towering gardens in the heart of a city. Despommier, who is working on a book on the idea, sees vertical farming as part of the answer to global warming, water shortages and inner-city health problems.

The key arguments for vertical farming are these:

  • Conventional farms waste water. Despommier says irrigation accounts for 70 per cent of worldwide water use, and much of that is wasted as runoff, but because it's contaminated with silt, pesticides and fertilizers, it can't be captured and reused. Vertical farms would grow crops hydroponically, in a water-and-nutrient solution, or perhaps aeroponically, using a mist of nutrient-laden water. The approach could grow the same crops with as little as 10 per cent of the water used in traditional agriculture, Despommier argues.
  • Vertical farms would make it easy to grow food without chemicals. There is growing concern about the environmental effects of pesticides and fertilizers used in traditional agriculture. Some see organic farming as the answer, others argue organic farming can't deliver the yields necessary to feed the world. But vertical farming would virtually eliminate the need for pesticides because air coming in could be filtered to keep pests out, and whatever fertilizers were used could be kept within the system and out of lakes and rivers.
  • Growing fresh produce in cities would make it more accessible to poor city-dwellers. As a public-health professor, this one particularly interests Despommier. "It's very difficult to find fresh produce in inner cities," he said, so people who live there tend to eat less nutritious foods. "The data is overwhelming," he added: If healthier food is available, people will eat it.
  • Growing food close to where it's eaten would reduce transportation needs, which would cut greenhouse-gas emissions. Reduced use of fossil-fuelled farm machinery would also help cut emissions.
  • Vertical farms would improve air quality in cities by consuming carbon dioxide and releasing oxygen.

All this sounds too good to be true — and some people argue that it is.

The arguments against vertical farming aren't as numerous as those for it, but one of them in particular stands out: Urban land is just too expensive for vertical farming to be commercially viable in cities.

"I think it's going to be really hard to make the numbers work out," said Ryan Avent, a U.S. blogger with an interest in urban land use and a contributing editor to The Economist magazine.

On his blog, Avent points out that steel-and-concrete buildings, without fancy finishing, cost $300 per square foot or more in large cities. That works out to about $13 million per acre, compared with $3,000 per acre for farmland in Indiana. 

Thanks to year-round production and other efficiencies, vertical farming can deliver up to 20 times the yield of traditional agriculture, says Chris Bradford, managing director at Valcent Products EU, a subsidiary of Vancouver-based Valcent Products Inc. The company provided the equipment for Paignton Zoo's vertical-farm experiment at no cost to the zoo, in order to demonstrate the technology. But even that impressive yield is nowhere near enough to cancel out the difference in land cost between basic farmland and a vertical farm building.

'I think it's going to be really hard to make the numbers work out.'—Ryan Avent, blogger

That's part of the reason Valcent doesn't see city-centre agriculture as a significant market for its vertical-farming technology, Bradford says. Rather, he envisions it taking root in low-rent industrial buildings on urban fringes, where land is significantly less expensive than downtown but transportation to urban markets is cheaper and faster than from rural farms.

Despommier concedes that suburban industrial areas might be the most promising sites for vertical farms. However, he also argues that there is disused land in most major cities that municipalities might make available below market cost.

"I can take you to a place in New York City that's five square miles of unused property," Despommier says, referring to Floyd Bennett Air Force Base, in the borough of Queens, which opened in 1930 as the city's first municipal airport, was later used as an air force base and is now a historic district managed by the U.S. National Parks Service.

Despommier says Vertical Farm Technology LLC, a startup he has founded to work on vertical farm projects, has spoken with officials in cities that have parcels of land like this in mind for vertical farming experiments. Universities could also run vertical farm experiments on their urban campuses, he says.

Still, while the idea of businesses growing food for profit in city centres seems dubious, Bradford does see a possible niche for downtown vertical farming — growing high-value produce for customers who will pay a premium for freshness. A vertical farm in a Manhattan high-rise, for instance, might produce herbs and salad greens for a handful of fancy restaurants close by.

He also suggests Valcent's systems might be used in climates — such as the Middle East — that are simply too hot and dry for conventional agriculture to work well.

"We have never suggested that it will replace conventional agricultural systems," Bradford says.

And whatever potential vertical farming has, it won't be realized overnight. Even Despommier, probably its most enthusiastic proponent, says the idea could take 50 years to take hold — but he does expect some significant experiments in the next couple of years.

Grant Buckler is a Canadian freelance writer.