What Is a Composting Toilet
and How Does One Work?

By: Jennifer Merrigan Environmental responsibility

With the increasing need to be more conscientious of our carbon footprint, it’s essential that we look into more efficient ways to help the environment and get rid of waste. In this guide, we’ll explain what a composting toilet is, how one works, and necessary upkeep to maintain your toilet.

What is a composting toilet?

A composting toilet is a dry toilet that breaks down human waste through composting—a natural process of waste decomposition. Most compost toilets don’t use water for flushing and are therefore called “dry toilets.” These toilets are different from pit latrines and arborloos, as those models use a different composting method.

A composting toilet consists of two elements: a place to sit and a collection unit. The collection unit consists of a storage chamber, a ventilation unit, a urine diverting system, and an access door for removing the compost.

Types of composting toilets

There are two main types of composting toilets: self-contained composting toilets and central composting toilets. With central composting toilets, you can choose between two styles: a one-pint flush toilet or a waterless toilet. Here are the main differences between the three.

Self-Contained composting toilets 

A self-contained composting toilet is a toilet system that’s installed directly into your bathroom and is available in both electric and non-electric versions. Here are some of its biggest benefits:

  • You don’t need plumbing in order to install this toilet, which makes installation quick and easy. The only major task involved is assembling the vent stack (which is typically included with your unit).
  • You don’t need approval from your state to have this toilet installed.
  • These units come with a bowl liner that can be easily removed, which makes cleaning easy.
  • Most self-contained toilet units have a high-gloss finish, making this toilet more attractive than other composting toilets.

Central Composting toilet systems

With a central composting toilet system, users can enjoy a traditional-looking toilet that functions similar to a regular toilet. This system is connected to a central composting unit located either in the basement or outside of the home. There are two major types of central composting systems:

  • One-Pint Flush—The more popular of the two, the one-pint flush style offers a similar look and functionality to a traditional toilet. This toilet system will connect a plumbing pipe to the composter.
  • Waterless—In order to minimize water output, a waterless option is available. This type of composting toilet works by connecting a larger pipe to the composting unit. As opposed to using water to flush the waste, the waterless central composting toilet system uses airflow to vacuum the liquid waste through a pipe. To mitigate odor, there’s a continuous flow of air drawing down through the pipe.

How does a composting toilet work?

Composting toilets use the natural process of decomposition and evaporation to recycle human waste. Of the waste that enters your toilet, 90% is water. That 90% of waste is evaporated and carried back into the atmosphere through a ventilation system and the remaining 10% of solid waste is converted into a useful fertilizer through natural decomposition. Note: most composting toilets use a slow composting process, which is where the compost heap builds up over time.

In order for a composting toilet to be effective, there needs to be a perfect balance between oxygen, moisture, heat, and organic material to create a rich environment that transforms waste into fertilizing soil. This balanced combination doesn’t just ensure the waste is transformed into fertilizing soil; it makes it so that the entire process is odor-free.

Additionally, when human waste is properly decomposed, the newly created fertilizer doesn’t create any type of pathogens or viruses—they will have been destroyed by the bacterial breakdown that takes place during the composting process.

The end result is a nutrient-rich fertilizer that can be used on plants and the base of trees. This process saves you money on fertilizer, helps reduce your own carbon footprint, and preserves the quality of water in your surrounding area.

What do you use in a compost toilet?

Most composting toilets use nothing and are considered “dry toilets.” They’re flushed using an airflow vacuum or a small amount of water to move waste through the pipe system and prevent any odor residue. Once the waste has entered the composting chamber, carbon additives like sawdust, coconut coir, or peat moss are added to absorb the waste and help the decomposition process. Because of the carbon additives that are added to your compost chamber, there should be no odor from your waste.

Can you use toilet paper with a composting toilet?

Yes, you can use toilet paper with a composting toilet. In fact, toilet paper is a source of carbon for the composting process. You don’t need to purchase special toilet paper for your composting toilet, although it’s recommended to opt for recycled materials.

How long until the compost is ready?

You’ll want to wait at least eight hours after the last deposit before dumping your compost chamber. It’s recommended that you dump your compost after every 60–80 uses (this equates to about a week). The size of your composting chamber will also determine how often you need to dump the contents.

Maintenance for composting toilets

While maintaining your composting toilet is surprisingly easy, there are several maintenance tips you should keep in mind. Most of them revolve around how to dump your composting waste and how you use your composting toilet.

Installation considerations

The ease of installation for composting toilets varies from product to product, as well as how you plan on using your toilet. For example, if you’re installing a composting toilet in your RV or tiny house, your installation may be as simple as placing your toilet wherever you want it to be and installing a ventilation system.

If you’re planning on installing a composting toilet in your home with a pipe that will divert your waste to another location, such as your basement or outside of your home, then you may want to review the installation guidelines thoroughly or call a plumbing professional to assist in the process.

Regulating odors

Carbon additives, the airflow system, and added liquid will move your waste to the composting chamber to prevent odors from forming. If your composting toilet does smell, it may be due to improper installation of your venting system.

The emptying process

Depending on how large your composting chamber is, you should empty your chamber around every 60–80 uses, or once a week. There are several ways to empty your composting chamber. If you’re in an RV park, there are several waste emptying facilities and treatment plants where you can safely empty your compost chamber.

If you plan on using your compost as fertilizer, research where you can place your composted material and if you can use it in your yard. If you’re staying in a single location for an extended period and are opting to use your compost waste as fertilizer, spread your waste in multiple locations, as opposed to a single location.

Is a composting toilet for everyone?

Composting regulations vary drastically depending on the state you live in, so be sure to review your individual state’s guidelines before purchasing a composting toilet. For example, Oregon now includes site-built composting toilets as an option instead of a traditional plumbing toilet.

Regardless of the regulations in your state, most composting toilet codes don’t apply to dwellings that also have flush toilets. Here are a few things to keep in mind when considering adding a composting toilet to your current home:

  • Make sure your composting area is on your property and you’re only transporting compost material on property lines you’re licensed to do so.
  • There are no restrictions keeping you from creating a compost pile in your backyard.
  • You have at least one flush toilet inside your home, as most United States building codes require every legally habitable dwelling to have one flush toilet connected to a sewer or septic system.

How much does a composting toilet cost?

The price of your toilet can depend on factors like whether you want a luxury composting toilet or a simple toilet for your RV, special features that come with the toilet, and where you’ll be installing it. In general, toilets can range from $100–$2,000. Consider where your composting toilet will be located, how you’re going to install it, how often you’ll use it, and any related maintenance costs.

While you may want to find the most affordable toilet on the market, keep in mind that this is a piece of your home that will be visited frequently so don’t be afraid to invest in a high-quality model.

Best composting toilets

Water consumption
Features
Product dimensions

Nature’s Head Self Contained Composting Toilet

Water consumption

Waterless

Features

Made in the U.S., stainless steel hardware, full-size toilet seat, assembles and disassembles in seconds, vent hose and fan included

Product dimensions

22 x 20.5 x 21.7 in

Sun-Mar Excel Self-Contained Composting Toilet

Water consumption

Waterless

Features

First self-contained composting toilet to be certified by the National Sanitation Foundation, claims to emit zero odors, completely water-free system

Product dimensions

31.5 x 22.5 x 31.5 in

Nature’s Head Dry Composting Toilet with Crank Handle

Water consumption

Waterless

Features

Hand crank agitator for fast composting, user-friendly, easy installation, vent hose, bottle cap, and power plug included

Product dimensions

19.8 x 20.8 x 20.5 in

Nature’s Head Self Contained Composting Toilet

Considered one of the most reliable choices for a portable, self-contained dry toilet,, Nature’s Head Self Contained Composting Toilet can be used in your RV, your houseboat, or in your home. Some benefits include eliminating all odors from waste and easy installation. Regarding drawbacks, some have mentioned that the compost created is less than desirable as opposed to a sawdust toilet.

Sun-Mar Excel Self-Contained Composting Toilet

The Sun-Mar Excel Self-Containing Composting Toilet is known to set the standard for composting toilets as it’s the first to be recommended by the National Science Foundation (NSF). The Sun-Mar Excel can easily accommodate three adults for continuous use or up to six adults for non-continuous use (such as those on vacation).

Most consumers that recommend the toilet boast of the heater that helps keep the compost box dry to avoid odor and to help move the decomposition process along, while others have complained that the drain overflow and vacuum pipe don’t work well.

Nature’s Head Dry Composting Toilet

Known to be the most reliable solution for eco-friendly personal sanitation, the Nature’s Head Dry Composting Toilet offers an innovative design that’s efficient and easy to use. Most consumers commend this product for its easy installation and maintenance, while others have complained about bugs being attracted to the toilet due to waste buildup.


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