The pie in the sky
• A self-sustaining "vertical farm" that grows crops using solar power, rainwater (collected in troughs at the base of the tower, as well as city wastewater) and geothermal energy (from plant waste turned into clean-burning fuel pellets).
Rapid urbanization. By 2050, the worlds population will have increased by 3 billion, requiring 20 per cent more land to grow food.
Extreme weather events (floods, droughts, monsoons) and blights are taking their toll, destroying millions of tonnes of valuable crops each year.
Iceland. The Nordic country already grows many of its crops in greenhouses using geothermal energy.
• Creating variable climate conditions on each floor to grow different crops. The first generation of skyfarms may grow only one crop, like lettuce.
• Light. The skyfarm concept relies heavily on light from a rotating solar panel on the roof, but the use of artificial light in darker winter months may result in crop damage and lower yields.
• It'll cost about $113 million to build a 21-storey facility that can produce as much food as a 420-hectare traditional farm and feed 35,000 people.
• Uses less water: 18 litres for every kilo of lettuce compared to 593 litres per kilo in traditional farming.
• Hydroponic tech can increase yields up to 23-fold over soil-grown crops.
What critics say
• The use of wastewater from the city's sewage system, which contains high pathogen and nitrogen concentrates, poses health risks.
The big hidden downside
• Mega-corporations (Dole, Kraft, Coke, McDonald's and others) are already sniffing around. Are we on the road to once again to our putting food security in their hands?