Urban warehouses, derelict buildings and high-rises are the last places you'd expect to find the seeds of a green revolution. But from Singapore to Scranton, Pennsylvania, "vertical farms" are promising a new, environmentally friendly way to feed the rapidly swelling populations of cities worldwide.

In March, the world's largest vertical farm is set to open up shop in Scranton. Built by Green Spirit Farms of New Buffalo, Michigan, it will only be a single story covering 3.25 hectares, but with racks stacked six high it will house 17 million plants. And it is just one of a growing number.

(READ the story from NewScientist)