A SLAM DUNK!

Are vertical farms the future of urban food?
A conceptual illustration of a vertical farm A conceptual illustration of a vertical farm. Photograph: www.odesign.com.au /Oliver Foster
With more mouths to feed and increasing demands on land, Duncan Graham-Rowe looks to see if high rise city blocks will be the source of tomorrow's supper

Duncan Graham-Rowe for Green Futures, part of the Guardian Environment Network
guardian.co.uk, Thursday 29 July 2010 10.20 BST

The vaults rose up as high as the city walls, bearing reeds richly bedded in bitumen and gypsum. The layered galleries peered each beyond its neighbour to reach the sunlight, and water drawn from the river was pumped through conduits up to the highest level. The topsoil was thick enough to root even the largest trees...

These were the renowned Hanging Gardens of Babylon, as described by the Greek historians Diodorus and Callisthenes, and the earliest example of vertical farming – at least according to Dan Caiger-Smith. His company, Valcent, is taking the concept into the 21st century, recently launching the first farm of its kind at Paignton Zoo in Devon.

It's a beguilingly simple idea: make maximum use of a small amount of space by filling glass houses with plant beds stacked high one above the other.

Financial and environmental pressures on modern agriculture have sparked new interest in vertical farming. With global population expected to exceed 9 billion by 2050, competition for land to grow both food and energy crops will become increasingly fierce. Four-fifths of us will live in dense urban areas, and increasing awareness of the carbon and water footprints of well-travelled food will have pushed locally grown produce even further up the list of desirables.

So it's easy to see the appeal of a system which, its proponents insist, can surpass the productivity of existing agricultural spaces by up to 20 times, while using less water, cutting mileage and energy costs, and delivering food security.

"It answers so many of the big questions of the future", says Caiger-Smith.

Valcent's system requires about the same amount of energy as having a home computer on for ten hours a day. That's enough to produce half a million lettuces a year – and, the company claims, seven times less than is required to grow the same crop on a traditional farm.

The 100 square metre farm at Paignton Zoo grows leaf vegetables for animal feed. It applies a technique called hydroponics, where plants are grown in nutrient rich solutions instead of soil. Stacked in trays eight layers high, the crops are continually rotated to ensure that all have adequate access to air and sunlight. The system also allows nutrients that have not been directly taken up by the plants to be collected and recirculated, along with the water, reducing usage and minimising waste.

This is just the beginning, says Caiger-Smith. His company now has more than 150 clients around the world queuing up to see how hydroponics could meet the needs of human food production, too.

How indeed. Inspiring concepts and artists' impressions abound, but with none actually up and running yet, how can vertical farms meet the impressive efficiency and production claims being made for them?

By cutting lots of corners. For a start, they remove the need for tractors and other fuel-dependent equipment. Distances to ship the produce from grower to retailer to consumer are also slashed. As Jeanette Longfield, Co-ordinator of the food and farming non-profit group, Sustain, puts it: "Intensive agriculture is currently entirely dependent on fossil fuels, from its use of nitrogen-based fertilisers to mechanical equipment, transport and refrigeration – and so urban agriculture really makes a lot of sense". In particular, Longfield sees "great potential for perishables that don't travel well".

Moreover, the traditional dependence of yield on the weather is taken out of the equation, offering greater security to the full supply chain.

Proven business models are still a way off. "It takes a stock market to build a high-rise," says Natalie Jeremijenko, an aerospace engineer and environmental health professor at New York University. She doubts that the income from vertically farmed crops would be sufficient to recoup the rent. But this hasn't stemmed her interest. Instead, she's come up with two designs to sidestep the problem: one is a small hydroponic rooftop pod with a curved shape to maximise exposure to the sunlight. The other is a vertical farm designed around a fire escape on an occupied high rise.

Sustain has also set out to demonstrate that urban land doesn't always come at a premium. The organisation has launched the programme Capital Growth, which aims to create 2,012 new food growing spaces in London before the city hosts the Olympics that year. The search encompasses "all kinds of nooks and crannies" – from school grounds and the banks of canals to roof terraces.

The other option is to simply do things on an industrial scale. Dickson Despommier at Columbia University, author of The Vertical Farm: The World Grows Up, believes there is scope to take vertical farming to an entirely new level, quite literally. He wants to create a new type of skyscraper to pierce the Big Apple's skyline – vast multi-storey buildings dedicated to vertical farming. According to Despommier, a single 30-storey building could provide enough food for 10,000 people.

And he's not alone in thinking big. Belgian architect Vincent Callebaut has drawn up plans for a huge tower, also in New York, on the city's Roosevelt Island (see 'Weak signals: how to track a changing horzion'). Callebaut's vision, dubbed the Dragonfly, is to create buildings with lush, fertile interiors that function as self-contained, sustainable eco-systems, producing food for their residents.

It's not just a flight of fancy. Will Allen in Milwaukee has already demonstrated the concept with a community food aquaculture system he calls Growing Power. This symbiotic cultivation system relies on aquatic life, such as tilapia fish and yellow perch, to redistribute nutrients. Waste products from the fish fertilise plants, while vegetable waste and worms from the gardens feed the fish. Both the vegetables and the fish are sold to local businesses at a marked up price, so that local residents can buy the produce directly from the farm at a subsidised price.

If vertical food does prove cheaper to produce and consume, then it's unlikely to face much opposition. In years to come, "locally grown" may mean just a few blocks from home.

• Duncan Graham-Rowe is a former staff writer for the New Scientist and a regular contributor to The Economist and The Guardian.

• Additional material by Anna Simpson, Deputy Editor, Green Futures.
http://www.guardian.co.uk/environment/2010/jul/29/vertical-farms-urban-food