Talk about turning lemons into lemonade: a Columbia University professor says inner city blight can be turned into bountiful skyscraper farms.

Dickson Despommier says one 30-story building could feed 50,000 people with hydroponicly grown food and zero carbon footprint. It sounds too good to be true, but Despommier is getting potential investors interested in building a prototype, at the cost of a billion plus dollars.

Having a vertical farm inside city limits makes sense because then you can reach the widest audience with the least amount of transportation. Perhaps the supermarket chains would be interested in footing the bill.

I've often thought that something has to be done with those decaying buildings that line the roadways in North Philadelphia and along the LIE in New York, but I never would have imagined a farm. Hydroponics has been around for decades, so I'm sure the technical challenges in managing a synthetic environment are still formidable. We wouldn't want this to become another Biodome II.