Photo of a SunMar Composting Toilet - courtesy of Buyer's Guide to Composting Toilets
Waterless, composting, alternative toilet types, brands, sources

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Composting toilet guide:

This article describes the nature of composting toilets, how they work, how they are used, where they can be used, usage restrictions, and different composting toilet types and features. We describe how to choose a composting toilet, what questions to ask, what features you need, where to install the toilet, how much space is neeed, elecricity, heat, special supplies, cleaning & service requirements. Bulk & mulch alternatives.

We define & describe just about every composting toilet type, feature, methods of operation, & maintenance requirements as well as costs. We list sources of various models of composting toilets and compare composting toilet model features, uses, and costs. We include a table of composting toilet supplies, uses, properties & prices.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Guide to Buying, Using, & Maintaining a Composting Toilet

L&T Duomatic Composting Toilet (Greece) - at InspectApedia.comWhat is a Composting Toilet?

A composting toilet is a self-contained unit (not connected to a septic or sewer system) which breaks-down and dehydrates human waste to a compost which can be added to soils.

Shown, the L&T Duomatic toilet produced in Greece and discussed in this article. [Click to enlarge any image]

The toilet will consist of a place to sit (which is likely to look a lot like any other toilet), a composting chamber which breaks down and sanitizes the sewage, and a drying chamber or tray which permits moisture to escape, reducing the sewage volume.

Composting toilets come in models which use a little water or no water at all, and in electric (heated and power-vented) models and non-electric models. Some models include electro-mechanical mixers which mix waste in with a mulch product to speed and improve the composting process

. Properly designed and installed the toilet is vented so that there are no abnormal toilet odors. Periodically the compost must be emptied and on occasion toilet components are cleaned.

People use the toilet in a normal manner, and modern composting toilets in fact look pretty familiar, resembling water-based toilets in general shape and comfort. Waste is mixed with a "starter mulch" to begin the composting process.

Composted waste is emptied from the toilet at intervals ranging from one or two months to 12 months depending on level of usage and toilet design.

Composting toilets which do not mix new human waste with material already being composted produce a compost which is easier and safer to handle. This is a reason that some models use multiple containers or compartments, though there are other solutions to this problem. If the visible portions of the toilet need cleaning, normal household cleaner and toilet brush are used.

Composting Toilet Selection Question List

The following questions one asks when considering installing a composting toilet are addressed in the article below:

Where are Composting Toilets Most Often Used?

Composting Toilets may be used where the water supply is limited or not available at all, or where a building owner for other reasons wishes to conserve water use. Other wastewater treatment will still be required for handling graywater from sinks and showers. Shown above is the SunMar compact composting toilet. SunMar composting toilets and toilet models by other manufacturers are described below.

Full-Time and Part-Time Usage Composting Toilets

The buyer should consider carefully their intended maximum usage level of the toilet before choosing a composting toilet model.

Full time composting toilets are intended to serve as the main toilet in a full-time occupied building (more than 5 days continuous use, for example).

Part time composting toilets are intended to serve buildings which are not occupied full time (that is less than 5 consecutive days) or by some manufacturers, these models are intended for use during limited hours per day (10 or less).

Electric vs. Non-Electric Composting Toilets

Electric models include heaters to aid the composting, possibly a power ventilation system, possibly a system which mixes air in with the compost to improve the aerobic bacterial breakdown of waste, and possibly a mixing mechanism to mix sewage with mulch to aid the composting process.

Non-electric composting toilets may also be vented but will lack a heater and power mixing.

Water and Electricity for Composting Toilets

Composting toilet models vary among waterless, low water, and foam flush units. Obviously a water-model requires a water source.

Composting toilet models also vary between models requiring electricity (typically 110V), battery operated (12V), possibly solar powered, and models which use no electrical power. Features such as automatic mixing, aeration, and vent fans will require electricity

The Composting Earth Closet: Antique Composting Toilet Photos

Antique composting toilet - maybe  (C)  MK

Sent to us by an Australian reader, and shown here are images of what we think is an antique composting toilet, missing some parts of course. Readers who have more to offer about this device are welcome to use the page top or bottom CONTACT link to send us information.

Below first photo: two large gear wheels mesh with and move a steel conveyor belt that moves waste to a mixing chamber. In our second photo, propellers (yellow arrows) driven by the rear conveyor gear (orange arrow) provide additional mixing of waste with compost, typically using a sawdust starter.

Antique composting toilet - maybe  (C)  MK Antique composting toilet - maybe  (C)  MK

Since earth closets incorporating moving parts have been described as early as 1881 it's certainly possible that the device above was a mechanically operated composting toilet.

Davey & Co. advertised a "self-acting" earth closet, according to - retrieved 2016/02/25 - Ed.

Automatic, Semi-Automatic, and Manual Composting Toilets

PHOTO of the Excel composting toilet by SunMar

A fully automatic composting toilet will typically control a heater, ventilating fan, and a mixer to mix sewage and mulch together. A fully automatic toilet mixes each time the seat is lowered.

A semi-automatic composting toilet will still use a thermostatically controlled heater, fan. But the sewage-compost-mulch mixer is manual, typically providing a handle that is turned a few times after each use of the toilet.

[Click to enlarge any image]

The compost process involves biological breakdown of the waste - a process that needs oxygen (air) heat, and some moisture.

Waste/compost/mulch mixing (the traditional "turning of the compost pile") is used to improve the aerobic breakdown of waste pathogens, to macerate the waste (which aids breakdown), to be sure that all parts of the sewage are heated and treated, and to speed the composting process.

Not all composting toilets use a compost/sewage/mulch mixing mechanism, and composting toilet manufacturers do not all agree on whether or not mixing is required. The Humanure Handbook by Joseph Jenkins has an article discussing this topic [] [Envirolet has posted his article at their website].

Shown at page top is the SunMar Excel™ composting toilet. SunMar provides low water and no-water composting toilets. Image courtesy of and SunMar.

Composting Unit Size and Features vs Maintenance Needs

Smaller composting units, especially smaller units which do not use heaters and aerators, because they risk unwanted liquid accumulation, insects, and nitrification of the waste, will require more maintenance and care than units which provide an aerator fan, heater, and compost mixer.

Toilet Trap/Bowl-Closure Methods

Because some folks don't want to look into the sewage/compost in a self-contained composting toilet, and also for odor control and sanitation, all composting toilets have some method of closing off the bottom of the bowl from the waste line or composting receptacle.

Some composting toilet models use an automatic trap closing mechanism which appeals to people who don't want to operate any unfamiliar controls on their toilet.

Other composting toilets use a manual valve to close the bottom of the bowl. The manufacturers of composting toilets which use a manual valve point out [Envirolet] that men who are accustomed to urinating while standing up will have to sit to urinate on toilets which provide an automatic bowl valve.

Watch out: we've come across composting toilet user reviews complaining that the bowl closing door design looked great (automatic when the seat was lifted) but proved flimsy or actually broke quickly when the toilet was in service.

Note: we have not quoted specific reviews griping about shoddy products, clogs, breaks, and snafus or poor service because of uncertinty about the review source, authority, etc. But it's worth reading a few of these when sorting out composting toilet features and maintenance and repair performance.

Composting Toilet Waste Process Methods - Batch vs Continuous

Composting of sewage in a composting toilet involves worm processing, micro-organism processing (bacteria, molds, and possibly other microorganisms) and dehydration by the evaporation of moisture.

The toilet manufacturer may recommend or provide a specific mulching product to aid the composting product and probably to aid in deodorizing.

Batch System Compost Toilets

A batch-system composting toilet interior contains multiple or change-out composting compartments. When a compartment (or change-out container) is filled with waste it is sealed and taken out of use to permit the sewage breakdown to continue. When the composting process is complete for a given container it is emptied (and presumably applied to soil in a legal manner) and the container is returned to use.

Continuous Composting Toilets

A non-batch, continuous composting toilet receives waste continuously into a single container. The composting procedure reduces the volume of the waste which is eventually (typically after 6-12 months) removed from the bottom of the container and is considered "fully composted material" which is then emptied (and presumably applied to soil in a legal manner).

Compost Toilet Installation Space

Be sure to review the installation requirements for the composting toilet you're considering. Some models require that the toilet be installed directly over the composting reservoir and others not; some models use a large reservoir below the toilet, others may be much smaller and self-contained.

This makes a big difference if you're considering a composting toilet in a one story building built on a slab, particularly if your toilet installation space does not include space for an along-side composting tank.

In a non-freezing climate it may be feasible to add-on a shelter against a building wall to contain the composting unit, but in freezing climates where the composter needs to be protected from freeze damage (varies by model) placing the composting tank outside the building envelope increases the installation cost as well as risks of freeze damage.

When planning for space for a central composting unit (using a composting tank that is separate from the toilet itself) remember that you're not going to just jam the composter into an inaccessible crawl area. Access needs to be easy, safe, and comfortable, as regular access will be required for cleaning, emptying, and other maintenance chores.

Compost Toilet Operating Requirements

Regulations and Standards for Composting Toilets

List of Sources for Composting Toilets and Composting Toilet Brand & Model Comparisons

Composting Toilet Product Index & Feature Guides

Airhead Composting Toilerts

Airhead composting toilet distributed in Australia by abetterwaytogo, cited at Airhead composting toilet distributed in Australia by abetterwaytogo, cited at

Above: two views of the Air Head composting toilet. [Click to enlarge any image]

Biolan Populett Composting Toilets

Biolan Composting Toilet, Finland - at

Biolet composting and waterless toilets

Photo of a Biolet composting ToiletBioLet Toilet Systems 830 West State Street Newcomerstown, OH 43832, Tel: 800-524-6538, Website:


Centrex Composting Toilets

Centrex 1000 composting toilet from SunMar Photo of the Centrex 2000 A/F central-flush waterless air flow composting toilet which uses
a below-floor composting drum - a composting toilet

Clivis Multrum Composting Toilets

Sketch of the design for a Clivus Multrum composting Toilet

CTS Composting Toilets

Photo of CTS composting Toilets - a bunch of them being transported


Eco Toilets - New Zealand composting toilets
Sketch of the Toatrone waterless composting toilet from Eco Toilets in New Zealand.

Carousel Composting Toilets - EcoTech

Photo of a Carousel batch process composting Toilet




Eco John Composting Toilets - U.S.
Photo of the EcoJohn Basic - A waterless separating composting toilet

Eco Toilets, Composting Toilets, New Zealand

Ekolet Dry Composting Toilets

Ekolet composting toilet, model for year round use - at contact Ekolet in Finland  - information given in our article

Dry toilets are in wide use in Finland, with usage increasing after a 2004 passage of a wastewater treatment regulation # 542/2003 and an update to the regulation in 2011, Finland rgulation # 209/2011 that address handling of wastewater in buildings that are not connected to a public sewer.

Envirolet Low Water & Waterless Toilets & Composting Toilets

Photo of an Envriolet self contained composting toilet

L & T Duomatic - kompostikäymälä Composting Toilet - Greece

L&T Duomatic Composting Toilet (Greece) - at

LetsGoGreen - SunMar Canada

Liberty Pumps composting toilets

Nature's Head composting toilets

Nature's Head composting toilet

Nature Loo Composting Toilets, Australia

Phoenix Composting Toilets

Separett Urine Diverting Composting Toilet

Separette urine diverting toilet at

Site-Built Composting Toilets

Shown below is a composting toilet system in use above Akaroa at the Hinewai Reserve (Maurice White Native Forest Trust) on the Banks Peninsula in New Zealand.

Using a combination of purchased and site built components this composting toilet serves hikers and visitors to the preserve.

Composting toilet, Hinewai Reserve, Akaroa New Zealand (C) Daniel Friedman

Separate toilet facilities or latrines for urine are provided for use if the liquid level in the composting toilet becomes too high but at the time we visited this facility a note from the management encouraged peeing into the composting toilet as the mixture was too dry.

Composting toilet, Hinewai Reserve, Akaroa New Zealand (C) Daniel Friedman Composting toilet, Hinewai Reserve, Akaroa New Zealand (C) Daniel Friedman

At above left is the box of dry plant material, of which a small handful is tossed into the composting loo after each use. At above right we see that this composting loo includes a ventilating fan that can be switched on if the composting toilet is a bit smelly.

Sun Frost Human Humus Composting Toilets

SunMar Composting Toilets

Photo of a composting Toilet

Sunmar Centrex 2000 or 3000 waterless toilet system at

Thetford Composting Toilets

Table of Composting Toilet Operating Costs, Choices, Supplies - do we really need to buy mulch or sawdust or other stuff?

Reader Question: What are the operating costs & choices for composting toilets? Are consumables really required for composting toilets?

Your web site has been very useful indeed but we remain uncertain about our choice. Are you aware of a composting toilet that uses water and standard house electricity for which there are no consumables necessary? if not is there a way of comparing the on-going costs of additives for these toilets? Thanks very much - A.D. - Canada

Reply: List of Composting Toilet Supplies, Costs, Features, Functions

I am not aware of any composting toilet design for which the manufacturer recommends no consumables whatsoever. The minimum consumable required is a bulking material. Sun-Mar and some others also offer enzymes, deodorants, and compost activators that may be optional.

Quoting from the Phoenix Composting Toilet System Instructions for Operation and Maintenance, and noting that opinions vary among manufacturers about the best and most easily biodegraded bulking material to use in a composting toilet:

Bulking material is necessary to improve drainage and aeration, and to provide extra carbon, thus creating conditions essential for composting. The right amount of bulking material gives the compost pile a crumbly, porous texture.

An inadequate amount results in a wet, pudding-like texture, puddling liquid, and anaerobic conditions that generate an unpleasant odor. [1][2]

"Anaerobic conditions" means more than just an unpleasant odor. It also means the system will lack aerobic bacterial action and biodegradation will not proceed properly nor adequately.

Keep in mind that the operating cost for a composting toilet depends not only on the cost of supplies but on the type of toilet selected (non-electric vs. electric, for example) and upon the level of usage and perhaps maintenance. That said, below we have begun a table of composting & waterless & low-water toilet system supplies, uses, & costs.

Table of Toilet Supplies for Composting, Low-Water & Waterless Toilets

The toilet supplies listed in the table below are available from the manufacturers listed in a product directory found in the article above, as well as from additional distributors located online.

Composting Toilet Brand & Supply Item
Quantity Properties Usage
Biolet Compost Starter Mix $30. 8 gal. bag

A specialized compost mix of peat and other natural organic materials help keep your BioLet composting toilet at its peak efficiency.

Formulated by soil scientists, this mixture provides the optimum balance for efficient composting.

1 bag will last 2 people using a BioLet full time for about 3-4 months.

add 1/2 cup of this compost mix after each fecal use



New Zealand

      nothing listed
Envirolet® Starter Mix Kit $32.
2 for $59.
1 bag of premix starter material and 1 paper mat activates the composting process. Recommended for seasonal start up of your Envirolet® composting toilet system or any other type of composting toilet system. not found
Envirolet Compost Accelerator




1 x 16 oz jar

Applied to Envirolet® composting unit once every two weeks with a small amount of warm water.

Helps accelerate the composting process in your system. Take advantage of the quantity discount!

Can even be added to your home or backyard composter.

16oz jar will last approximately 9-12 months when using 1 tablespoon every 2 weeks with a warm cup of water.
Envirolet Daily Mix Reusable Pail $43.

56 Cups Daily Mix in Reusable Pail

Daily Mix is specially formulated for daily use with Envirolet® Composting Toilet Systems.

Improves composting and is recommended instead of peat moss. All natural material.

1/4 cup per user of Daily Mix every day evenly over compost
Envirolet Daily Mix Refill Pak for above item $94.

6 bags. 168 cups see above see above
Envirolet Air Solution Kit



3 gel cassettes per kit

Cassette is placed inside system between Aeration Basket and shell of body.

Helps ensure a fresh outside scent. Particularily helpful in low lying areas or areas where trees may result in a downdraft.

Each cassette will last approximately 30-60 days

Nature Loo
Nature Flush Enzymes


$32 AUD 1L

$140 AUD 5L
1L or 5L of concentrate, dilute 20 parts water to 1 part enzyme concentrate .

Enzyme Concentrate –
To speed up the composting process and provide a fresh fragrance with the push of a button, enzymes can be sprayed into the chamber.

In the case of the Compact toilet you can either add these manually using a hand held domestic spray flask or by purchasing our micro dosing pump kit, which produces an evenly distributed spray directly onto the contents of the chamber.


Kits contain a micro flush foot pump, storage container, pipes, nozzles and enough enzyme concentrate for 4000 flushes.
Phoenix composting toilet bulking mix see note at right  

The best bulking material is dry planer shavings from a white softwood
such as pine.

Do not use shavings from decay resistant woods such as cedar or redwood: this material will reduce the composting rate.

The bulking agent must have a physical structure that resists compaction so that air voids will remain open.

Do not use large wood chips, wood waste from treated lumber, or materials that form a mat, such as long grass or leaves.

Dry pine shavings often are sold as bales of animal bedding.

Add one to two gallons of bulking material
through the toilet or upper access door for every 100 uses.

Add one to two gallons of bulking material
through the toilet or upper access door for every 100 uses.

Sun-Mar® Compost Sure - BULK $75 list

avail at $60
One Bulk package = 5 boxes of 8-gallon (30L) bags

Comprised of peat moss & chopped hemp stalk. Quoting: Compost Sure consists of coarse peat moss and chopped hemp stalk.

Compost Sure has an added advantage over homemade bulking material - hemp.

Hemp will decompose where wood shavings and peat moss do not - giving your compost a longer residency time!

More importantly, it saves you the time of making your own mix.

1 cup of compost mix per person per day or 1 cup of compost mix for every bowel movement.
Sun-Mar Compost Sure Blue - BULK $75-$90 One Bulk package = 5 boxes of 8-gallon (30L) bags

Bulking material containing 100% hemp stalk.

Designed especially for central systems with low-flush toilets in addition to garden composters.

The hemp stalk breaks down quickly while offering good porousity and keeps the compost supplied with carbon.

?? - copy from above 1 cup of compost mix per person per day or 1 cup of compost mix for every bowel movement.
Sun-Mar Compost Quick Spray



12/ 16oz. bottles of spray enzyme. Enzyme liquid accelerates the composting action, leaving you with a perfect finished compost every time. It can also be used as a cleaner for either your bowl liner (for self-contained models) or your toilet (for Low Flush systems). 3-4 squirts of nozzle before rotating drum. We estimate that translates into 200+ squirts/bottle or 25 drum rotations.
Sun-Mar Microbe Mix $17. 16 oz jar Super-biologically active bacteria which will recharge your compost.  


1. Prices are rounded to nearest dollar

2. Fast dissolving toilet tissue & other supplies are excluded from this list unless specified as required by the toilet manufacturer.

3. Bulk additive for composting: reading reviews of what works and doesn't work for people we note that

- Sun-mar advised an unhappy owner of a Centrex composting toilet that their soggy waste mixture was caused by failing to use the proper mix of sawdust and peat moss - (retrieved 2/24/2014 2014)

- Watch out: do not use home-made bulk composting remedies like wood shavings or wood chips; you're likely to clog and possibly damage the composting mixer as well as to see poor results in the field.


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