Dry Composting Toilets
A Dry Composting Toilet is a toilet that does not use water to take the waste somewhere else; instead, it also allows natural processes to produce useful compost after a resting period. The main job of a composting toilet is to contain human waste and create conditions for rapid decomposition – including any pathogenic organisms – into humus; a safe stable soil-like substance. Unlike a septic tank, which contains water, a composting toilet system relies on unsaturated, dry conditions, where aerobic bacteria and fungi break down wastes, just as they do in a yard waste composter.
The significance of a dry composting toilet lies in the fact that not only does it conserve water, a fast depleting natural resource, and create a usable organic fertilizer to enrich the soil -- it also reduces the sewage load in cities. They are of even more significance in distant regions that are not connected to a main sewage line.
Many desert communities have traditionally made use of such toilets. In Ladakh, for instance, there are double-storeyed toilets, with the composting unit underneath. The floor of the toilet is liberally covered with sawdust and straw and has a hole for waste to be dropped into the composting unit. Every day, the straw and sawdust is swept into the composting unit through the hole, and a fresh layer is added. After a year, the contents of the compost pit are spread across the fields.
 Characteristics of Dry Compost Toilets
- Dry composting toilets normally consist of two chambers -- one that is in use, and the other for composting.
- Contrary to popular belief, they do not smell if used properly. All they need is a vent, drain for excess liquid and a handful of soak (sawdust, straw or ash) after every use.
- The soak is very important as it provides enough carbon to the mix, and balances it with the nitrogen of human waste. If the mixture has too much nitrogen, the bacteria will emit a lot of smelly ammonia. Also, the soak allows oxygen into the pile, and absorbs liquid. This allows the pile to decompose aerobically to produce nitrates, phosphates and sulphates. Without a soak, the pile will decompose anaerobically and produce methane, ammonia and hydrogen sulphide – all smelly and not very useful.
 Benefits of Dry Composting Toilets
- The solid waste is dealt with on site, instead of ending up as sewage, or worse, in waterways.
- They save water – you don’t have to use one resource (pure drinking water) to flush away another (fertilizer)
- The organic waste matter is allowed to go back to the soil where it belongs, improving soil structure and nutrition
- No chemical cleaners or bleaches are used in the toilet
- As long as the decomposition is aerobic, there will be no greenhouse gas emissions
- No electricity needed
- Low resource use -- no pipes are needed to transport waste to a sewage farm, and no truck needed to remove solid waste.
 Using a Compost Toilet
There is no doubt that using a compost loo is not as simple as using its flush-and-forget Western counterpart. Here are some things to keep in mind --
- Check the toilet everyday to ensure no problems are developing.
- Ensure that there's a bucket with 'soak' (e.g. sawdust) next to the loo.
- Rake the composting compartment every couple of months to speed up the composting process.
- Use the compost from your composting toilet with care -- it is all right to use on trees and bushes, but it is advisable not to use it in the vegetable patch.
 Did You Know?
- In the East, particularly in China and Japan, human waste was considered a rich resource. So much so that travelers were often enticed by farmers to use their way-side privy, and in cities human waste was collected and transported out into the neighbouring farm land. It was such that several visitors staying in an inn would receive a discount in payment simply by exchange for their collective deposit of humanure!
 See Also
- Helena Norbert-Hodge, 1991, Ancient Futures: Learning From Ladakh, Oxford University Press
- Forum on Dry Compost Toilets
- Compost Toilets
- Indian Water Portal
- Why Use Composting Toilets?
- The Design of a Composting Toilet