How does a waterless toilet work?

How does a waterless toilet work?
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Waterless toilets are important in areas where water is scarce, mainly because they do not use water to dispose human excreta.

However, their adoption is still limited globally due to misunderstanding on how they work.

If used well, waterless toilets provide an ideal option for hazard-free disposal of human waste in water deficit regions.

In this article, we’ll discuss how the following waterless toilets work:

  • Composting toilets
  • Freezing toilets
  • Incinerating toilets
  • Urine-Diverting Dry Toilet (UDDT)
  1. Composting toilets

The most popular type of waterless toilets is the composting toilet. A composting toilet essentially uses aerobic processing to break down human excreta.

Bulking agents, such as sawdust, peat moss, or coconut coir, are usually added to enable thorough aerobic break down.

The bulking agents are also useful in the absorption of liquids and prevention of odor. The product of the decomposition is referred to as compost, and can be used as fertilizer.

Main parts of a composting toilet

Most composting waterless toilets have two main components in their structure: first, is the sitting unit which has the toilet bowl; second, is the collection or composting unit.

The composting unit has three main parts.

a) Chamber where composting takes place and acts as a store for the waste.

b) A ventilation system designed to collect leachate (leachate is the excess liquid that accompanies the fecal matter during excretion).

c) A door that enables access to the compost for disposal.

  • How composting toilet works

Composting toilets use aerobic natural organisms to break down human waste.

Oxygen, right temperature, and moisture are essential for this to happen. Eventually, the excrement is transformed into compost that is odorless.

A composting waterless toilet usually has three main functions:

i) Efficiently evaporate moisture

The excreta entering the composting toilet is more than 90% water, which evaporates and is channeled out via the ventilation system.

In some composting toilets, the feces and urine go separate ways, which makes it easy for moisture to be removed from the system.

Also, most modern composting toilets have a heating apparatus to accelerate the evaporation process.

It’s worth mentioning that while fast evaporation is desirable, entirely drying out the compost can affect the break down process.

Therefore, a good compost should be kept moist, not wet, for optimal functioning.

ii) Decompose the excreta without producing stench

Thereafter, bacteria work on the hard matter in the composting chamber, breaking it down.

Although this process can be completed naturally, it can take a long time and generate strong stench, making your house smell like a dumping pit.

Therefore, bulking agents are normally added to create conducive environment for decomposition and eliminate any odor.

iii) Ensure the completed compost is safe to use and handle

After the composting process is complete, it should be safely disposed, something that makes most individuals squeamish.

Understandably, handling human excreta is difficult for most people. However, with an efficient composting toilet, you’ll not see any signs of human waste or odor—you’ll only get a rich product you can use as fertilizer.

  1. Freezing toilets

In a freezing toilet, the waste is frozen. The freezing stops bacterial growth, and stifles odor.

These kinds of waterless toilet use electricity and are portable.

As such, freezing toilets have to be plugged into an electric power system to function.

  1. Incinerating toilets

Incinerating toilets dispose human waste by burning.

The incinerator sets fire to your waste or urine and burns it to ashes.

The ash is harmless due to the high temperature used for the burning process.

They are fueled using electricity, gas, diesel, batteries, or other energy sources.

Most incinerating toilets are used just like the normal flush toilets, but the lid has to be closed before flushing. The flushing apparatus is a huge screw that pushes the waste into the incinerator.

After you’ve done your business, you close the lid and dial incinerating button, and the magic happens behind your back.

  1. Urine-Diverting Dry Toilet (UDDT)

Urine-diverting dry toilets (UDDT) separately collect urine and feces. This kind of waterless toilets has a specially designed seat or squatting pan to separate the collection of urine and feces.

The diversion of urine is intended to reduce odor and enable the easy management of excreta.

Most modern UDDT systems are made up of four basic parts:

a) Specially designed toilet seat

b) A single or two vaults for collecting and storing feces

c) Urine piping leading to a collection tank

d) A ventilation pipe

c) Option of an anal cleansing area

  • How a UDDT works

Once you defecate in a UDDT, the solid waste and material used for anal cleaning drops into the designated chamber.

After each use, it is critical that the fresh solid waste is covered with material such as lime, wood ash, or saw dust. This kind of material is meant to soak up moisture and combat odor.

There are four different kinds of feces management in UDDT systems.

i) Feces dehydration done in dehydration vaults

ii) Feces management that incorporates external treatment. This kind of feces management is undertaken in single vaults that have interchangeable containers

iii) Feces mineralized in shallow pits

iv) Feces composted in containers (When used, feces should be kept moist)

For feces management to work well, solid human waste has to remain dry in the vaults (dry feces are also odorless).

As such, separating urine from the feces and protecting the deposited feces from rain is important.

It is the dryness in the vault of the UDDT system that reduces the amount of pathogens in the feces. The reduction of pathogens in the feces eases its handling.


Waterless toilets can work well if everyone is educated on their use. It is such kind of actions on the use of waterless toilets that can make the difference in the hygienic disposal of human waste.

Better still, it is important to have as many people as possible understand their functioning to bolster waterless toilets adoption, especially in areas where water is a challenge.