28 February 2009
A reality - not just a concept - at least in Sweden, where 135,000 of these are currently in use. The systems keep toilet contents separate from the greywater of other household (sink, tub) use, and further separates urine and feces for individual recycling purposes.
Nightsoil has of course been used for millennia to enrich soil. Gardeners, even in industrialized countries, have saved urine in jugs for application to their garden plots; they just don't talk about it in public. The toilet above uses modern technology and design to facilitate these age-old processes.
Long discussion at the New York Times. Photo and image credit to this German corporate website, where there is further commentary.