With their towering skyscrapers, cities such as Dubai and Abu Dhabi seem as far from the image of rural life and open fields as you could imagine. For one leading US academic, though, they represent the future of food production, with "farm-scrapers" not just housing people and offices but diverse crops including peaches, date palms, tomatoes and Brussel sprouts, to name but a few.
Also known as "vertical farming", the concept of high-rise city greenhouses, powered by solar energy and urban sewage, will be the way to feed the urban world, according to Dickson Despommier, a professor of public health in environmental health sciences at Columbia University in New York. "A 30-storey building, one New York city block in footprint, could feed 50,000 people," says Prof Despommier. "That means fruit, vegetables, meat, fish, poultry - and fresh water to drink."
He singles out the Gulf as the region where vertical farming could first become a reality and says he has already had preliminary inquiries from investors in Abu Dhabi. The combination of year-long sunshine and an increasingly urban population makes the region ideal for the first project, he says. A microbiologist by trade, Prof Despommier, has spent the past 10 years looking for a solution to feeding an increasingly overcrowded planet. Feeding the seven billion mouths on the planet today already requires a land area equal to the entire continent of South America. And that area is increasing.
"In 50 years there will be another three billion people. We've already used up 80 per cent of the land available for agriculture and this will require another 40 per cent," he says. "There isn't another 40 per cent." That is where Prof Despommier's skyscraper greenhouses come in. Each offers a sealed, controlled environment eliminating the possibility of disease or pest attack, and the need for harmful agricultural chemicals. Special lighting mimics the properties of sunlight so plants can continue to photosynthesise and grow at night. Crops can be cultivated 365 days a year, oblivious to outside weather conditions. This continuous production means that every acre indoors is equivalent to between four and six acres of outdoor farmland.
Electricity for light and heat is generated by renewable energies, such as solar power and wind turbines - and by burning waste stalks and roots from the farm in high-temperature incinerators. Self-cleaning window glass - which has a coating of titanium dioxide to break down dirt - ensures crops receive maximum sunlight. Efficient insulation minimises heat loss. The crops are grown hydroponically, in nutrient-rich water rather than soil. Building vertical farms in or close to cities means that urban treated liquid waste known as grey water can be used for irrigation.
What is more, plants act as natural filters, giving off pure water vapour, which can then be captured. So the farms double as huge water purification facilities. "New York City generates a billion gallons of grey water every day," says Prof Despommier. "Put that into a vertical farm and you could recycle all of it as drinking water." Virtually all crops can be grown in a vertical farm, including vegetables and grains, as well as fruits.
Livestock would be housed in the lower floors, with tanks for farming fish, and open areas for rearing chickens for eggs and poultry, or sheep for meat. "Vertical farming is a novel approach that makes use of solar energy; the one, and only, significant renewable energy the Earth has," says Dr Don Erbach, president of the American Society of Agricultural and Biological Engineers.†"It could contribute significantly to sustainable food production."†
It makes ecological sense too. With 80 per cent of Earth's population set to live in cities by 2050, urban farms would drastically reduce the need to transport food. And as traditional farmland returns to nature, biodiversity will be restored to formerly monocultured areas. Even biofuel crops, like oilseed rape, can be cultivated indoors. How much will it all cost? Prof Despommier says with an initial investment of US$50-60 million he could have a prototype vertical farm up and running in three years. Local investors are said to be interested, but a deal has yet to be brokered.
The farms could offer much-needed food security in the area's arid climate, as well as a way to generate fresh water that is much cheaper than desalination. "The Masdar eco-city, for example, is going to require something like this," says Prof Despommier. Cary Mitchell, professor of Horticulture at Purdue University, in Indiana, agrees the region would make a good site. "In light-limited locations, vertical farming will require expensive supplemental electric lighting and this is the main factor limiting its profitability. But sunny Abu Dhabi may be a notable exception to this rule."