Dry (Urine-diverting) Toilet

 What is a dry toilet?

  A dry toilet is an above ground urine-diverting latrine, where the urine and feces are separated to reduce smell and provide a constant source of fertilizer in the form of urine.  The dry toilet features a special toilet seat which captures the urine and sends it down a separate pipe to a container where it can be collected and stored until use.  The urine is 97% sterile and has 95% of the nitrogen that is excreted. As long as it is not contaminated with feces, it can serve as an excellent fertilizer with no treatment except dilution.

The feces drops to a container or chamber below the toilet where it is mixed with ash or soil after each use (it is good to use ash when it is readily available as it will raise the pH which kills some of the pathogens in human feces).  The lack of urine, in addition to the ash and soil, keeps the contents of the toilet dry which reduces smells and helps to kill pathogens.

The dried feces can either be stored in a chamber below the toilet for one year and then removed and used as fertilizer or removed regularly from the toilet and added to a secondary compost heap where it can be composted for at least a year before being used as a fertilizer.

What is special about dry toilets?

Attractiveness:

When offered a choice of sanitation options families often prefer the dry toilet because it is attractive and can be installed either inside or outside the house. These toilets are also valued for their reduced flies and odors that result from keeping the feces dry.

Efficiency:

Dry toilets are also very valuable in farming communities or for those with backyard gardens, because they produce a constant supply of fertilizer in the form of urine, instead of the semi-annual compost obtained from the Fossa alterna. Urine has high levels of nitrogen and phosphorous and functions in very much the same way as chemical fertilizer. The photo on the right shows an experiment in Peter Morgan’s yard in Zimbabwe where corn was grown in unfertilized soil (L) and soil fertilized with urine (R)  Though very effective at increasing agricultural yield, chemical fertilizers are produced using fossil fuel energy and often must be transported long distances for use.  These factors, in addition to the environmental effects of over-fertilization in industrialized countries, make the long term, widespread use of chemical fertilizers unsustainable.  Urine, on the other hand, is a locally produced resource that is free, effective and can be an environmental pollutant if allowed to run into water sources instead of being recycled through the soil.

Groundwater protection:

Because dry toilets are above ground structures, none of the contents of the latrine get into the water table. For many years development agencies have been promoting deep pit latrines, sometimes up to 20 feet. When these latrines are constructed near water supplies or in areas where the water table rise to above the level of the latrine, pathogens and nutrients from human wastes mix with the water supply creating environmental and public health problems. Arborloos and Fossa alternas are less likely to pollute water supplies than deep pit latrines because they are very shallow pits.  However, in areas with a very high water table or where flooding is common pit toilets in general may be appropriate and dry toilet systems should be considered. Even modern flush toilets can cause serious water pollution, as almost all of the sewage in the Asia, Africa, Latin America and the Caribbean is discharged into rivers or oceans without treatment.

 Where are dry toilets used?

 Dry toilets are used primarily in Sweden, Mexico, and South Africa, though the technology is rapidly being adopted in throughout the world. Germany and Finland have also initiated large programs and the International Dry Toilet Conference will take place in Finland in August 2006.  These toilets have proved to be effective in both rural and urban areas, and the potential for both indoor and outdoor installation makes them attractive to a broad sector of society.

 To see how to build a dry toilet, view the step-by-step construction of the first dry toilet in Milot, Haiti.

(Back to ecological sanitation)