Leading Compost Toilet Information and Advice

A compost toilet must be the toilet of the future.


When you consider that the average American uses 7,665 gallons of water (that's approximately 2,400 cases - 24 count - of bottled water) each year just flushing the toilet, it makes you wonder about an alternative.

We're hear to teach you everything we know about one alternative - composting toilet systems.


You're going to learn what they are, how they work, the various types, how to make them, their advantages and disadvantages, and whether or not they're safe.

"The current technology of "waste disposal" is still fighting
a war against nature, built on fragments of nineteenth
century science not yet integrated into an understanding
of life processes as a unified, but cyclical, whole.
"

Van Der Ryn - The Toilet Papers



What is a Compost Toilet?

A composting toilet is a receptacle, and controlled processing unit, for human excrement, toilet paper, and carbon additives (i.e. bulking material including peat moss and wood shavings). Composting toilets are referred to by several different terms, including biological toilets, dry toilets, and waterless toilets. Although these toilets can be used anywhere (especially portable composting toilets), the majority are currently used in seasonal homes, homes in remote areas, and recreation areas.

compost toliet There are two primary objectives that need to be met by a compost toilet:

1. To contain and immobilize, or destroy, pathogens that could potentially harm humans. This is to be accomplished in a manner that eliminates contamination of the environment and minimizes harm to its inhabitants.

2. To transform the nutrients in humanure into an inoffensive, and reasonably dry, end-product that can be handled with minimal risk. This end-product can then be used as a soil amendment for horticultural plants and trees*.

*Please refer to our "Are They Safe?" section below for proper use of this end-product.

How Do Composting Toilets Work?

The operating principles of a compost toilet are almost identical to those used in your backyard compost bin. The goal is to create an environment in which beneficial microbes (i.e. bacteria and fungi) will proliferate. These microbes are the workforce behind the breakdown of your humanure. To create an ideal microbial environment in your toilet, you'll need moisture, oxygen, and heat.

Moisture - The moisture in a compost toilet comes from urine as well as the solid excrement. If not properly controlled, the moisture levels can get too high, resulting in anaerobic composting and an unpleasant odor - just like in your garden compost pile. Most manufactured composting toilets do a great job of regulating moisture levels using fans, evaporation chambers, and separation trays. Click here if you would like to see an example of an evaporation chamber in a self-contained Sun-Mar composting toilet. The addition of bulking agents (i.e. peat moss, coconut coir, and wood shavings) also help to control moisture levels.

Oxygen - The oxygen in a composting toilet system comes from several sources, including automatic mixers, pile-leveling devices, tumbling drums, and manual turning. Bulking agents also provide pore space for air to enter into the composting mix.

Heat - The heat in a composting toilet system can come from the pile itself (i.e. the heat generated by the microbial activity) as well as an electrical or solar heater. Solar composting toilets are a great way to take an already eco-friendly invention - the composting toilet - to the next level of environmental stewardship.

As you can see, the means of providing these three composting principles can be quite variable. To understand the operation a little better, it's best that we look at the various types of compost toilets that are available.

how to build composting toilet


Types of Composting Toilets

Compost toilets can be divided based on several different criteria. However, we believe it's easiest to think of the different types of toilets by first looking at how they process the waste, and then considering how they are built.

1. Processing - How is the waste processed?

All composting toilet systems use an active or a passive process to breakdown their contents. An active system can be compared to an outdoor, dynamic composting pile - these both produce heat. Active composting toilets rely on various features, such as fans and thermostat-controlled heaters, to provide aeration and heat to the composting waste. A passive system, on the other hand, can be compared to an outdoor, static composting pile - these decompose over a longer period of time in cooler environments.

All composting toilet systems use a batch or a continuous method of processing. Batch composting means that the catchment receptacle is filled, removed, and allowed to decompose and cure without the addition of more excrement. Thus, a toilet using a batch composting process typically requires more than one catchment chamber (i.e. composting reactor). Continuous composting means that the catchment receptacle is constantly receiving new waste materials, while at the same time producing finished product. A toilet using a continuous composting process usually requires only one catchment chamber.

Refer to the picture at the beginning of this section, for an example of building a composting toilet that uses both batch and passive processing.

2. Assembly - Who built the composting toilet system?

Was the system manufactured and purchased, or was it site-built using composting toilet plans?

Manufactured Systems

    Self-contained composting toilet systems describe the models in which the toilet seat and catchment chamber (i.e. composting reactor) are in one unit. These are ideal for situations where space is limited or you don't want to spend time feeding pipes from one area in your house to another. Some examples of self-contained units are the Sun-Mar composting toilets shown here, and the BioLet composting toilet shown here.

    Centralized composting toilets are those models in which the toilet connects to a composting catchment chamber that is in a different location (e.g. basement or outdoors). These units are also known as "remote" composting toilets. There are several different types of centralized units including the vacuum- and micro-flush models. Some examples of centralized units are the Sun-Mar composting toilets shown here, and the Envirolet composting toilet shown here.

    There is one other type of manufactured composting toilet system we like to discuss, however, it can come in the form of a self-contained or centralized unit. We are talking about the dry compost toilet, or what some people call a waterless composting toilet. Waterless composting toilets rely on proper air flow and ventilation to dry the materials in the toilet. These units have generated some controversy; because there is concern that they may not reliably kill all harmful pathogens in human excrement. Please visit this page to learn more about the controversy surrounding waterless composting toilets.

If you would like to learn more about the pricing of various manufactured toilets, please visit our composting toilet prices page. This page also provides composting toilet reviews, including what we believe is the best composting toilet on the market.

Site-Built Systems

    In-House composting toilets are those units that are designed to be used indoors, and they are built by none other than you (or another one of your compost junkie friends). These systems are usually self-contained and are quite simple to build. All you'll need are a few basic hand tools, some wood, a couple screws, and a bucket. To learn how to build a compost toilet, including composting toilet plans, head over to our how to build a composting toilet section.

    composting outhouse Out-House composting toilets are those units that are designed to be used outside. These units are also built by you. However, they tend to require more planning and labor than in-house toilets, so be sure to call upon your friends for some help.

    The picture to the right is a great example of out-house composting toilet. Most composting outhouses are raised off the ground, or built on a slope, to allow for easy emptying and turning of the waste.

To help ensure you get the most out of your new homemade composting throne, we have created a poop-errific tips and tricks page. There are also some excellent do-it-yourself, compost toilet books on the market. These books will provide you with more information on this topic, including "how to" plans for more complex toilet designs.

IMPORTANT - Before installing any of these Site-Built systems in or near your property, please be sure to consult your local by-laws and regulations. Oftentimes, it can be quite difficult to get a permit for these site-build systems from your local health agents, and we wouldn't want any %#@# hitting the fan.

The Advantages and Disadvantages of a Compost Toilet

There are far too many pros and cons to composting toilet systems to post them all on this page. For instance, one advantage of these systems is that they reduce the need for transportation of wastes to treatment centers. However, one disadvantage of these systems is that they require more maintenance than a flush toilet, therefore, more responsibility and commitment by their owners. Since this list is quite long, we decided to give it its own page.

Are Composting Toilets Safe?"

Yes, assuming you take all necessary precautions. The key is to ensure all of the principles of regular composting are met. You must ensure proper moisture, oxygen, and temperature levels. Another element you must always consider is time. In the world of composting, the rule-of-thumb is: the more time, the better. The longer the microbes in your compost have to break down the waste materials, the lower the risk that any harmful pathogens will survive.

If you are planning on purchasing a manufactured compost toilet, be sure it meets all of the mandatory standards in your area. For instance, in the United States, the standard governing minimum materials, design, construction and performance of composting toilet systems is the American National Standard/NSF International Standard ANSI/NSF 41-1998: Non-Liquid Saturated Treatment Systems. Boy, what a mouthful! Other certification and standard programs include CSA and cETL-US.


Lastly, the resulting end-product of a compost toilet is a stable, soil-like material called "humus." In most American states, it is illegal to use this material in your gardens. Therefore, it must be either buried or removed by a licensed waste hauler. Please check your state and local regulations for details.


On that note, we want to CAUTION you against the use of this humus in edible gardens. We're going to repeat that...DO NOT USE THIS HUMUS IN EDIBLE GARDENS! If you are going to use this humus in your gardens, be sure you only use it around your ornamental trees and shrubs and that you bury it.

Okay, that's way too much talk about the loo, we gotta run...