sustainable design (like permaculture) mandates that 'nothing goes to waste' including 'waste', i.e., there is nothing that is waste, i.e.^2, everything has a use.
a potentially queasy problem in going off-the-grid is the management of human waste (note - not disposal, but management)
lets get to the evolution of the toilet design at pR.
the simplest toilet in the world in the hole in the ground.
this hole is connected to a tank/pit which collects the faeces/urine/water.
in cities with areas not connected by sewarage systems, this tank is called the septic tank and the municipal authorities arrange to empty them at designated intervals.
in villages, sulabh's bindeshwar pathak and safai vidyalaya's ishwarbhai patel have pioneered the two-pit latrine system aka pour-flush-compost latrine.
this is how this system has been installed at pR. the pic on the right shows the top covers of the two pits.
the key short-coming of this system, is the potential contamination of the ground water (by leaching) as the faeces is mixed with the flush-water and the urine (total approx 3 litres per use).
also, in the case of heavy flooding, there is a risk of leakage into the over-ground fresh water systems (lakes, tanks, etc).
it was clearly evident that we would need to address the above shortcomings.
1. the faeces should be kept separate from water and urine.
2. the faeces collection should be safe from flooding.
enter the urine diverting ecopan from paul calvert's eco-solutions.
here it is installed at pR.
this is the indian style version. the wooden frame (pic on right) is for holding.
explanation of this design (refer to the pic on the left).
1. the middle of the long pan is for the urine colletion.
2. the lid (with red knob) covers the pit into which the faeces drops (there are 2 pits on either side of the urine collector - the knobbed one is in use and the other is closed).
3. the short pan on the left of the pic is for washing the backside post dropping.
this entire system is mounted (with brick and mortar) at a height of around 2 feet. so the faeces collection pit is above ground.
sawdust is used extensively to line the bottom of the pit prior to usage and after each use to cover the faeces. this will absorb excess moisture and prevent odours, etc.
the urine and wash water could be directly led to plant beds just outside the toilet.
Note: - we will be running the urine through a charcoal bed as we feel that it is too concentrated to be directly given to plants.
now the important part - what happens to the faeces.
the capacity of the collection pit is approx 5 cu ft.
and 5 people can use it for over 6 months without even hitting 50%.
at this stage, the in-use pit will be closed (after generous dumping of sawdust) and the sitting position is reversed and the other pit will be start being used.
within 6 months, the faeces in the closed pit will have decomposed and can be easily and safely removed and used as manure (very high quality).
the key shortcoming of this system is the physical discomfort involved in the perpendicular swivel move to reach the backside wash pan. and not too appropriate for saree wearers.
the Ecosan urine diverting toilet from biome solutions is a better design with the backside wash pan comfortably placed just behind the faeces pit. so a simple shuffle of around 3 inches behind will place the user right above this pan.
this design will be optimised shortly in Stage 4.