IMHO, the volunteering institute will extinct really quickly if TSHTF, labor for food and slavery will take it's place. Same fate upon dumpster divers. The food is not growing there by itself.

Is there any perspective for an at home hydroponics for urban survival?

Also I'm totally disagree with your mushrooms hatred. It's a very good source of nutrition, but requires some more practical knowledge and theory than dumpster diving. This book is all one may need to get started: http://www.amazon.com/Mushrooms-Demystified-David-Arora/dp/0898151694