Introducing permaculture

Topic: Connections
Subtopic: The web of life
Age: 7 - 12
Holistic Planning: Hand
Details: List all the inputs and the outputs for a common human food (e.g. a can of juice), get creative, see how far you can go back (with inputs) and how far you can go forward (with outputs). Can you make it (this food or a replacement for it) a closed loop system (where the outputs from one thing become inputs for something else)?