Here’s a very good video showing cutting edge technologies that make rooftop gardening profitable. At 19:54 they show how they’re making compost from food scraps very quickly in a machine.
Rooftop gardening is a simple idea that could help billions of people worldwide. It’s actually an ancient idea that’s already common in Japan, Singapore and Taiwan. Rooftop gardens are gaining traction in other places as well. The concept involves growing food on top of flat roofed buildings, primarily in urban areas where growing space is limited and the need for fresh food is greatest. France has just signed into law that all new commercial buildings incorporate green roofs.