Friday, March 11, 2011

Composting Toilets in Bayan Ulgii (Day 13)

Designing composting toilet systems for Islamic cultures is a delicate matter that demands diplomacy; Moslem belief holds that human organic waste matter is dirty and is something best dealt with by putting it out-of-sight and out-of-mind. 

Most households have pit latrines dug into the furthest corner of the family compound, and where the family has sufficient resources, further steps are taken to hide it from view (such as placing it where the entrance gate swings open so that it can only be seen when the compound is secured at night).  For most of the year, the sewage matter is frozen and so does not create an unpleasant odour or attract flies (though to visiting foreigners, squatting above a frozen pile of faeces pointing at your bum like Vlad the Impaler can be somewhat disconcerting), though during summer the paying a visit to the faecal soup outhouse is a decidedly ordeal.

Apparently, there is a city sewer system of some sort (though I haven't yet figured out how it works or where it would flow to, that is, when it is not frozen), as the apartments (and thankfully, my hotel) are equipped with working flush toilets.

In the lowest neighbourhoods of Ulgii City, pit latrines are dug approximately three meters deep.  The water table there lies at four.  That's not a lot of margin for error.

Q & A time is spent with the class to elicit an urgent response to design solutions to the challenges of dealing with human poo & pee: If 40,000 residents of Ulgii City are poo-ing and peeing in pits dug 100cm above the water table, how safe is the water you drink?

With that in mind, parameters and examples are given for designing alternative systems for managing the settlement's organic human waste:



  •  Waste is a resource that hasn't been successfully utilized in your system yet.
  •  How can the outputs of one element in your system become the inputs for another?
  •  Separate liquids and solids.
  •  Manage and process waste on-site.


  •  Nitrogen-rich liquid plant fertilizer.
  •  Safe to use immediately on plants (pee in a different spot each time to prevent 'burning' plants).
  •  Use later by diluting 10:1 water (suitable for drip-irrigation systems).
  •  Mulch pit can be used to compost urine at approx 25:1 carbon: nitrogen ratio.
  •  Do not use as liquid fertilizer if you are sick.


  •  Must be processed before it can be safely used as plant fertilizer.
  •  Heat to at least 60C for several house to kill pathogens(i).
  •  Compost for at least 2-3 years to completely break down waste material.
  •  Only apply processed humanure to tall crops (eg beans, other climbers, corn, fruit trees).
  •  Cover soild waste material after each visit to latrine with 'carbon material' to mask odour & begin composting process.

Possible design solutions:

  •  Separate liquids from solids using separate pit latrine / mulch pit system.
  •  Males can simply pee in a different spot around the garden each time they relieve themselves (not a good idea in winter, unless you want a yellow skating rink in your hasha).
  •  Bucket system: separates liquids & soilds, must be emptied into drip irrigation or mulch pit (liquid) or composting humanure heap (soilds).
  •  Revolving pit latrines: alternate between three or four shallower pits annually, allowing unused pits to break down.  Composted matter can then be harvested before pit is put back into use every third or fourth year.
  •  Large scale toilet system (eg for school): solar composting toilet.  Two toilet blocks are built and alternated annually.  A slope is used to transport solid waste matter down and away from the drop zone.  Carbon material is dropped into toilet pit after each visit to mask odour & aid in composting process.  Toilets are built above a 'solar digester', which is oriented to maximize solar gain and heat up.  Solar chimney vents high above usage zone.[see sketch]


Photo: Composting solar toilet design.



(i) ’Humanure Handbook’ by Jospeh Jenkins

(ii) Disclaimer: this information is given for educational purposes only and is not to be construed as professional design advice.  Consult a licensed architect or professional composting toilet systems specialist before implementing your own composting toilet system.

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