A Columbia professor believes that converting skyscrapers into crop farms could help reduce global warming and make New York cleaner. It’s a vision straight out of Futurama—but here’s how it might work.

http://nymag.com/news/features/30020/

I love how "Wastewater taken from the city’s sewage system is treated through a series of filters, then sterilized, yielding gray water—which is not drinkable but can be used for irrigation. (Currently, the city throws 1.4 billion gallons of treated wastewater into the rivers each day.)" -this isn't just growing vegetables, it is an urban battery, taking waste and solar energy and producing food, clean water and electricity.