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How Do Composting Toilets Work: Explained by Pros

how do composting toilets work
Written by Kai Michel
Last Update: August 10, 2023

If you’re looking for a safe and easy way to dispose of your liquid and solid waste, then you need a composting toilet. These toilet systems allow you to generate manure for your garden in an eco-friendly way. But, you’ll only enjoy these benefits if you know how a compost toilet works and how to use it.

If you’re asking how do composting toilets work? This guide will provide you with enough clues to help answer the question

How Do Composting Toilets Work?

How Do Composting Toilets Work

Composting toilets rely on the processes of evaporation and natural decay of human wastes. In case you’re asking how does a composting toilet work by evaporation? Here lies the answer.

The entire human waste that enters the toilet is about 90% water. This water is converted to air (moisture) which passes through the vent into the atmosphere. The other waste which is solid is converted to fertilizer for the garden.

The whole processes of decomposition take place in the chambers. This ensures that you have a complete and odor-free decomposition. The decayed human wastes from the compost toilet are free of disease-causing germs.

But before we discuss composting toilets and how they work, let’s see their basic function s first.

The Essential Functions

A composting toilet system will perform these processes as they function :

1. Compost the Solid Waste Without Odor

Although solid wastes break down on their own over time, this may lead to foul smell. This odor can make your home uncomfortable and also make you sick.

So, how does composting end the odor? A composting toilet needs a peat mix to hasten the decay of the solid waste. This bulk material may be additives like sawdust and popcorn.

A peat mix ensures that the final waste is odorless and safe for use. They allow the free flow of oxygen through the waste. This, in turn, helps to improve the growth and action of bacteria in decomposing the waste.

Sometimes, you can add the coffee grounds to your toilet to improve the smell.

2. Evaporate the Liquid

As we mentioned earlier, the bulk part of the waste is made of water, thus the need for quick evaporation. Most composting toilet systems come with outlets for urine. With this, more liquid will be evaporated at a faster rate.

Sometimes, you can remove the liquid to be used in the garden. The vent system is for the escape of the liquid into the atmosphere.

Besides the vent system, there are small heating systems that provide warmth. This is what makes the liquid to evaporate quickly. But, there is a need for the solid waste to keep some moisture which aids its quick decay.

3. Produce Safe and Easy to Handle Compost

One of the things that you’ll consider before installing your composting toilet is how and where to empty it. It is true that human waste is among the most difficult things to handle. Yet, a good and working compost toilet should provide a nutrient-rich and safe waste for your garden.

To overcome the fears of frequent emptying of the waste, it’s important to buy a compost toilet that with the size that is easy to manage. Sometimes, you can get one that will be only be emptied at most twice in one year. This allows the toilet to work on the waste until it becomes safe enough for your garden.

Working Principles of a Composting Toilet

The most efficient composting toilets come with three chambers namely:

  • Chamber 1: The Composting Chamber

So, how does the composting chamber of composting toilets work?

Here, waste and bulk materials enter the composting chamber through the waste inlet. You’ll need to aerate the mix by turning the drum using the hand lever by the side of the toilet. The opening of the inlet closes while you turn the drum to ensure that the waste does not fly-off.

So, how do you empty the waste from the composting chamber? By freeing the drum locker and rotating the drum in a backward manner you’ll empty the compost into the collector or drawer.

  • Chamber 2: The Evaporating Chamber

It is better if a little moisture remains in the compost. Liquid from the bowl passes through the liquid inlet into the evaporating chamber. Air and heat systems in this section help to provide the needed environment for the quick evaporation of the liquid. Thus, any liquid that does not get into the solid waste section will go into the evaporating chamber.

So, how does the evaporating chamber of the composting toilet work?

The liquid will first get to the evaporating tray before it enters the actual surface for evaporation. The function of the tray is to aerate the liquid and also increases the surface area for timely evaporation. You can take out the evaporating tray for cleaning through the drawer at any time.

In most composting toilets, a heater is provided to speed up the process of evaporation. This heating element is controlled by a thermostat to enhance its function . The heater is usually placed at the bottom of the evaporating chamber. Here, it keeps the floor of the chamber warm but retains moisture in the compost.

Where there is no electric heater in the evaporating chamber, the overflow drain must be connected. This is to assist the vents in improving the evaporating process.

  • Chamber 3: Finishing Drawer

The finishing drawer allows the decomposing process to finish before the introduction of fresh waste. The drawer ensures that the composts are dried before they’re taken out. When the waste is completely dried, it can be removed and handled with ease. So, the finishing drawer serves as a reservoir for the composts until the processes of decay are completed.

Benefits of Composting Toilets

Some of the outstanding benefits of using a composting toilet include:

  • Odorless

Composting toilets do not produce an offensive odor as regular toilets. The smell from regular toilets is as a result of the mixture of liquid and solid wastes. The composting toilets work to remove this offensive odor by using a special technology.

This technology is to separate the urine from solid waste. Also, it includes built-in vents that send the odor outside and lever mechanisms.

  • Water and Energy Conservation

How do composting toilet save water? Since they don’t need water to flush the wastes, the scarce water is used for other purposes. Now, you’ll spend less on water and energy bills.

Also, you’ll not be increasing the volume of wastes in the general waste tank which costs lots of money and energy to maintain.

  • Zero Need for a Septic Tank

You’ll save the money that would go into building and maintenance of septic tanks. Sometimes, where the number of users is much especially during camping, the septic tank would be emptied more frequently.

This is a huge financial burden which is eliminated by using a composting toilet.

  • Fertilizer

The composts manure contains all the essential nutrients that will enrich the quality of your soil. This means you’ll be saving the money that you’d spend on fertilizers. Besides, they don’t degrade the soil as most organic fertilizers do.

This means you’ll spend less, yet produce high-quality crop yield.

  • Easy to Install

All composting toilets can be installed without the services of a plumber. The process of installation is very straight and easy. All you need do is follow the instructions provided by the manufacturer.


You can use composting toilets in places with inadequate water supply, camps, and rural areas. They help to reduce the level of pollution of water and the environment. Also, composting toilets allow you to dispose of both liquid and solid wastes without using a septic tank.

Knowing about composting toilets and how it works will help in your decision about the type of toilet to buy.

About the author

Kai Michel

Hello, this is Kai, addressing homeowners in need of some help with their home renovation projects. I’ve worked on numerous toilet repair projects over the years that incorporated a wide variety of tasks, from repair to renovation and maintenance. Besides acquiring a degree on the legal codes and procedures, I gathered vast insights into bathroom settings, toilets, showers, fittings, and other household appliances, fixtures, and components. This helps me guide my clients through their home improvement and interior development plans. Since maintenance is my area of expertise, I can assist people in all phases of the actual ‘improvement’ process. To get my messages even further, I contribute to this site through my blog posts. Check my content here for expert suggestions!

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