Closing the Loop on Phosphorus

About half of humanity now lives in urban environments and this is increasing rapidly.
To make cities more sustainable, source separation of materials and recycling must become standard practice. The principle nutrients – nitrogen, phosphorus and potassium – recycle in nature, but human intervention has created a linear, nonrecycling, open-ended system.

Link: Ecosanres fact sheet 4. Closing the Loop on Phosphorus (PDF 380 kB)