GreenCities

Hi,

From my work at sustainable urban water systems, including dry sanitation and separate urine collection I would be interested to know whether urine is an acceptable fertiliser to you.

To collect urine separately in what we call Urine Diversion Dehydration Toilets (awful name, UDDTs) has the advantage to improve composting of faeces and to lead to clean urine, which, after some storage time, is hygienically safe and contains substantial amounts of nitrogen, phosphorus and potassium. It may also contain endocrine disruptors, though, if they have been consumed in the first place.

To make sense this should be used as fertiliser without too much transport, thus right at the place of production in town. If that is possible, such dry sanitation systems could replace wet sanitation, saving a lot of water and energy, reducing infrastructure cost and complexity, protecting the environment from nutrient emmissions into water bodies and providing fertiliser at the place where the food is needed.

Looking forward to your point of view and valued recommendations.

Martin

At Sirius EcoVillage in Massachusetts, there are composting toilets with separate urinals that divert to 55-gallon plastic barrels. These are periodically emptied onto large amounts of sawdust from the shop and micro-mill. The sawdust serves as a medium for holding the liquid so that it does not rapidly infiltrate through the soil profile, which would otherwise have been a loss of the urea's nutrient content. The sawdust also balances the C/N (Carbon to Nitrogen) ratio so that the highly nitrogenous urea doesn't "burn" the plants or throw the nutrient balance off.

The other main way of capturing nutrient value from human detritus (while conserving water) is, as you may know, intensive biological wastewater treatment, or the Living Machine. This is an ecologically engineered ecosystem that sequesters nutrient assets from sewage while performing tertiary-level treatment. This solution is appropriate for larger-scale communities and cities where "manual" separation of waste and on-site use is a less desirable option, and sewer systems are already in place.

An ideal Living Machine is located at Findhorn community in the UK, where, due to the community's existing ecological lifestyle choices, the influent sewage is not tainted with persistent pollutants, and the effluent water that comes out of the Living Machine after treatment is of potable quality!!

Even if effluent from such systems is not completely potable, it may be suitable for irrigation.

More on Living Machines can be found on Wikipedia, an article of which I wrote the bulk.