How Does Composting Toilet Work?

The understanding of how a composting toilet works is one of the greatest ideas you may ever come across. In fact, it is something that may leave you confused while trying to figure out how it actually works. It is unbelievable but true that a composting toilet works in the same way just as the natural process in the environment outside there.

This natural is artificially enhanced to develop composting toilets. However for everything to work as expected, all the necessary conditions must be available in correct proportions as in a natural environment. There are three main conditions which include; Oxygen, moisture and heat.

composting toilet work

source: wikipedia

The other two factors which are also important are the presence of an aerobic bacteria and adequate organic material of which in this case is the human waste. For your better understanding, am going to split the whole unit in to three different sections. The sections are; the compost chamber, evaporating chamber and the finishing drawer.

This way, I believe that you will be able to answer the question of how does composting toilet work. Let’s now have a look at how each of the three chambers operate one-by-one.


Compost Chamber

This is the first chamber of a composting toilet and is housed within the Bio-Drum. This chamber works by ensuring that an ideal environment for breakdown of human waste is available. The Bio-Drum achieves this by keeping a correct balance between Oxygen, organic matter, moisture and warmth.

The drum has an inlet at the top through which the waste material enters. At this stage, you will need to mix and aerate the components by rotating the drum continuously for some time. You will achieve this by turning the handle on the side of the unit.

One good thing as you rotate is the automated closure of the inlet door so that your work is made easier. This is very important as it ensures that the compost is safely kept within the drum. Thereafter, you may now want to empty the Bio-Drum but believe me not, it is easier than what you can possibly imagine.

Yes it is true, because it is one of the simplest operations on a composting toilet. All you need to do is to release the drum locker before you can rotate the drum backwards. Just by doing this, you will be surprised to see the drum’s inlet door reopening automatically and the compost dropping in to the finishing drawer.

The following are the four main roles of the compost chamber;

· Removes the odor of human waste with the help of aerobic bacteria whose operations are odor-free. Therefore regular rotation of the Bio-Drum is necessary for uniform supply of Oxygen. However if you fail doing this then the anaerobic microbes which produce bad odor would take over.

· Keeps the moisture levels within the range of 40%-60%. Anything below 40% slows down the process while above 60%, Oxygen which is required by the aerobic bacteria is driven out. Compost chamber controls the moisture levels by draining excess liquid in to the evaporating chamber and also by supplying correct amounts of heat to avoid unnecessary evaporation.

· Supplies Oxygen which is a key ingredient for the bacterial breakdown. You should therefore maintain a steady Oxygen supply by rotating the Bio-Drum as I stated earlier.

· Maintains the recommended amount of warmth. The heat energy required is generated by the microbes since their operation is an exothermic one.


Evaporating Chamber

It is the second chamber within the entire unit. Just as I stated earlier, it receives the drainage of excess liquid from the Bio-Drum. In electrical units, the liquid is warmed to speed up the rate of evaporation.

Remember that for maximum evaporation then three conditions must be met. First, there must be a large surface area then adequate heat and moving air. It is such a wonderful thing that a composting toilet has been designed in such a way that meets them all.

Excess liquid draining from the drum first fall on an evaporating tray and finally on to the main evaporating surface. The evaporating tray increases the surface area for evaporation, traps any solid waste material and oxygenating the drained liquid too.

In order to achieve an optimum rate of evaporation then heating is boosted by a 110v electric model. Such model has a heating filament whose temperature is kept constant by a thermostat. To achieve its maximum performance, the filament is sealed underneath the evaporating chamber.

In case the toilet unit is not electric then overflow drains are connected though the liquid would still partly evaporate through the vents.


The Finishing Drawer

Just as the name suggests, this is where the final operations take place. The finishing drawer is the collection vessel for accumulating the compost resulting from the system. To move the compost in to the finishing drawer, rotate the drum backwards and remember that this the same operation that is used to empty the Bio-Drum.

Once the drawer is full it is pulled off the unit and then the compost transferred before it can be reinserted for subsequent collection.


The finishing drawer serves the following functions in a composting toilet;

· Completes the whole process by isolating the compost from fresh waste in the drum. This facilitates the prevention of any form of contamination.

· It offers a temporary storage facility and gradually dries the newly formed compost before it can be removed from the unit. The drying is facilitated by a stream of dry air which passes through the drawer continuously.

· The finishing drawer makes it easier and safer removing the formed compost.

· It is where the sanitation process takes place. Sanitation is very important since it ensures that the compost is free of any dangerous agents which may cause infections. This is why the compost obtained from a composting toilet is always safe for other uses such as application as manure.



finalized compost. Source: wikipedia


This kind of technology is indeed a powerful environmental protection tool that is worth being adopted. What a wonderful end product, a product of huge economic value. The resulting compost has a great performance and is one of the highly recommended agricultural manures. Truly, your life is safer with a composting toilet.

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