The Economist takes a look at vertical farming:
The idea is that skyscrapers filled with floor upon floor of orchards and fields, producing crops all year round, will sprout in cities across the world. As well as creating more farmable land out of thin air, this would slash the transport costs and carbon-dioxide emissions associated with moving food over long distances. It would also reduce the spoilage that inevitably occurs along the way, says Dickson Despommier, a professor of public and environmental health at Columbia University in New York who is widely regarded as the progenitor of vertical farming, and whose recently published book, “The Vertical Farm”, is a manifesto for the idea. According to the UN’s Population Division, by 2050 around 70% of the world’s population will be living in urban areas. So it just makes sense, he says, to move farms closer to where everyone will be living.
It takes about a tablespoon of diesel fuel to move one pound of freight 3,000 miles by rail. So, reducing food-miles doesn’t pay off.
While growing food hydroponically in the controlled environment of a greenhouse may make sense, stacking the greenhouses does not, because — you may be surprised to learn — plants need light:
Indeed, even in today’s single-storey glasshouses, artificial lighting is needed to enable year-round production. Thanet Earth, a 90-hectare facility which opened in Kent in 2008 and is the largest such site in Britain — it provides 15% of the British salad crop — requires its own mini power-station to provide its plants with light for 15 hours a day during the winter months. This rather undermines the notion that vertical farming will save energy and cut carbon emissions, notes Mr Head, who has carried out several studies of the idea.
What might make sense would be planting crops on a steep slope facing south, for more direct sunlight.