How Does A Composting Toilet Work? (Detailed Guide)

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Composting toilets aren’t for everyone, but there are many scenarios where having a toilet with composting capabilities can be beneficial.

But before you go ahead and buy one or start your next DIY project, it’s a good idea to know the answers to questions like what is a composting toilet? How does it work? And what are the benefits?

That’s exactly what we’ll cover here in this detailed guide to composting toilets and how they work.

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How Does a Composting Toilet Work?

The exact process for “how does a composting toilet system work?” depends on the type of toilet in question, like whether it’s a self-contained or central system. However, the general steps are similar for all composting toilets, and the main thing to remember is that liquids have to be separated from solids.

To make that happen, here are the general steps involved in how a self composting toilet works:

The composting chamber is filled with a carbon material, like dried sphagnum or coconut fiber.
After waste is deposited into the toilet, the liquid waste is separated from the solids through a straining process. Usually, the liquids drain into a container that can be removed and emptied out while the solids move one to the composting chamber.
The solids mix with the compost materials - typically, this is done manually by turning a handle outside of the chamber so that the materials inside the chamber can be combined.
Once the toilet's chamber is full, the liquids can be disposed of, and the solid compost can be used according to the Department of Health regulations in your area.

As mentioned before, the specific steps depend on factors like toilet type and composting material used. To give you a better understanding of what’s involved in composting waste, here are a few more guidelines for specific composting toilet models/types:

The Nature Head Compost Toilet
When looking at the steps for "how does a Nature's Head composting toilet work?", it becomes evident that this is one of the best waste composting systems because it's easy to use. It's a self-contained toilet, using 2 different containers to separate liquid waste from solid waste.
The Sun Mar System
The process for “how does a Sun Mar composting toilet work?” is very similar to Nature Head. The company’s self-contained systems are all-in-one units that are easy to use and install.
The RV Compost Toilet
The answer to "how does a composting RV toilet work?" depends on the system type. Generally, RV toilets are self-contained, so the toilet seat and bowl are directly connected to the composting chamber.
The Portable Compost Toilet
Portable toilets are great for camping, and what better way to get in touch with nature than by creating compost? Since self-contained systems are the smallest and most compact, that’s generally what portable means.
The Tiny House/Boat Composting Toilet
Just like with an RV waste composting system, self-contained systems like the Nature Head or Sun Mar are great for tiny houses and boats.
The Waterless Composting Toilet
Actually, just about all composting models are waterless. The lack of water/liquid is what makes the composting process possible. So the answer to “how does a waterless composting toilet work?” is the same as any of the previous models listed. That’s why these toilets are often referred to as "dry."

What Is a Composting Toilet?

Just like any other toilet, a composting toilet is responsible for discarding our waste. But unlike traditional toilets, these work to transform solid waste into compost rather than just flush it away.

With the help of an oxygen-rich environment and aerobic bacteria, composting toilets can break down waste so that it can be added to the compost pile.

Another name for composting toilets is "dry toilet," and that's because most of them don't use water for flushing. Because of the lack of water, human waste is able to go through the composting process, which eventually leads to the decomposition of organic material.

Different Types of Composting Toilets Explained

Self-contained composting toilet (AKA Active):
The composting system is contained within the toilet itself, usually positioned directly beneath the bowl. This is very common for RV toilets and also great for boats and tiny houses, but not as common for larger residential homes.
Central or remote composting toilet
With this type of toilet, the waste is directed to a central composting location. This could be outside, in the basement, etc. With central/remote composting, it’s possible to connect multiple toilets to the system, so it’s ideal for larger homes.
Slow composting toilet (AKA Moldering)
As opposed to active toilets, slow composting toilets are more passive in performance. Usually, they’re designed in a way where waste can be isolated and slowly go through the composting process, which takes a lot longer with this type.
Vermicomposting flushing toilet
This type of composting toilet involves introducing earthworms to promote composting. There's a filter bed where solids accumulate; then the liquids drain down so that only solids are left, allowing the worms to do their thing.

Basic Components of a Composting Toilet

For a composting toilet to work properly, 2 main components need to be present:

1
The Compost Chamber
2
The Aeration Unit (AKA evaporation chamber)

The composting chamber is where the waste is collected, so it is directly connected to the base/seat of the toilet. This is where the waste and compost mixture combine together, and it’s where the decomposition process begins.

The point of the aeration unit, also known as the evaporation chamber, is to keep the compost moist but not overly saturated. In this second chamber, excess liquids are strained out and evaporated away so that the composting process can happen successfully.

While these are the main components, there are also a few more things necessary for composting to happen, like an exhaust system to get rid of odors, a ventilation system to help support the growth of aerobic organisms, and a method for withdrawing the compost when it’s ready.

Pros & Cons of a Composting Toilets

While there are many benefits to composting our waste, there are also some drawbacks:

Pros

Easy Installation
Great for areas without access to septic or existing plumbing systems
Cheap DIY alternatives
Preserves water – great for areas with water scarcity
Free compost – great for areas that use organic alternative soil
Odorless – many systems are designed to eliminate odors

Cons

Requires consistent maintenance
Can be unhygienic, hazardous, and unsafe to use if not properly installed and maintained
Might be more expensive than low-flow models

FAQs

Do you have to empty a composting toilet?

Yes, you will have to empty your composting toilet, but the good news is that it’s not as messy or unhygienic as you might think. Most systems are designed for easy clean-up and emptying.

Because the solids take time to compost, you’ll be emptying the liquid waste most often. One really great way to dispose of this is to use it as a plant fertilizer since it’s high in nitrogen content. However, just be sure to dilute with water beforehand. For solid waste, just dispose of it by adding it to your soil or compost pile.

Can you pee and use toilet paper in a composting toilet?

Yes, most composting toilet systems allow for urine (there are a few exceptions, though). These toilets are designed to divert the liquid waste into a separate chamber while moving the solid waste to the composting area. Compostable toilet paper is recommended, though all toilet paper will break down relatively quickly.

How much do composting toilets cost?

It depends, especially if you choose to build your own composting toilet as a DIY project. For a popular model like Sun Mar or Nature’s Head, expect to pay anywhere from $1000 to $2000.

How long does a composting toilet take to work?

This depends on the composting material used, but it could take anywhere from 3 weeks to 2 months.

How often do you have to empty a composting toilet?

This also depends, mostly on the amount of waste that is going in the toilet. If just one person uses the toilet, the bin will have to be emptied less often than if 3 or 4 people are using it.

Do you need electricity for a composting toilet?

Not all models need electricity, but many of them do use it to enhance the composting process. Airflow is an important component, so utilizing electricity is great for running a small fan to create better ventilation. Some systems even include a heating element to help promote good bacteria and kill harmful pathogens.

Conclusion

There are a lot of benefits to composting at home, like enriching the soil and “helping retain moisture and suppress plant diseases and pests.” The EPA also says that it’s great for promoting “the production of beneficial bacteria and fungi that break down organic matter to create humus, a rich nutrient-filled material.”

No matter your reason for choosing to use a composting toilet, just realize you're doing something great for the environment. The other good news is that modern composting toilets are easy to use and not overly complicated.

Ian Haynes

Ian Haynes is an expert writer who has successfully deployed over 500 plumbing pages and other related content. He has an excellent understanding of home plumbing issues and translates his experiences via Plumbing Lab so readers can have a better understanding of common household problems. Outside of his work, Ian likes exploring Brooklyn with his Labrador.