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Buyer's Guide to Composting Toilets - Are They A Septic System Design Alternative for Difficult Sites? InspectAPedia®  -     Guide to types, brands, and sources of composting toilets Where to buy composting toilets Comparison of different composting toilet designs/models

This page 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 list sources of various models of composting toilets and compare composting toilet model features.

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. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted.

Use of this information at other websites, in books or pamphlets for sale is reserved to the author. Technical reviewers welcomed and are listed at Reviewers.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

What 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. 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.

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.

Automatic, Semi-Automatic, and Manual Composting Toilets

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. 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 [www.jenkinspublishing.com] [Envirolet has posted his article at their website]. Shown here is the SunMar Excel(TM) composting toilet. SunMar provides low water and no-water composting toilets. Image courtesy of naturalhome.com and SunMar.

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.

Composting Process Methods

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).

Composting Unit Size and Features Affect 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.

Compost Toilet Installation Requirements

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.

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.

Compost Toilet Operating Requirements

• Ordinary toilet tissue can be used
• 120V electricity is required for some, not all models of composting toilets
• Ambient temperature in the room where the toilet is used (at least for some models) must be above 64 deg F when the toilet is being used. At least some models permit the temperature to drop (presumably below freezing?) during periods when the toilet is not in use. Composting is unlikely to proceed at low temperatures, a condition which may affect the level of usage allowed and the length of time for composting to complete.
• Periodically the composted waste is removed for disposal. It may be placed around trees and flowers or shrubs, but the owner needs to comply with local codes in this matter.
• Occasionally the exposed parts of the toilet will receive normal cleaning. Don't use bleach, which in a composting toilet would damage the composting organisms and may stop the composting process. Because most composting toilets are made of either plastic or fiberglass use of abrasive cleaners is probably a bad idea as well.

Regulations and Standards for Composting Toilets

The U.S. standard for composting toilets is NSF (National Sanitation Foundation) Standard 41. Some, probably not all, models advertised have been tested to determine if they meet this standard. In Canada, the CSA- has adopted and also certifies composting toilets to meet National Sanitation Standard (NSF-) Standard-41.

The following is from: New York State Appendix 75-A.10 Other systems

These units shall be installed in accordance with the manufacturers instructions. The units shall have a label indicating compliance with the requirements of National Sanitation Foundation (NSF) Standard 41 or equivalent. Only units with a warranty of five years or more shall be installed.

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

* Biolet Swedish composting toilets ranging from fully automatic electric composting BioLet 60 XL (4 people full time use) Composting toilet prices: $2000. U.S. to a non-electric BioLet 30 NE model (3 people full time use) $1400. U.S. Smallest model: $1000. * BioLet XL composting toilets available from BioLet (link above) and from EcoTech (link at left - EcoTech is a supplier of composting toilets including the BioLet series) are intended for cottages, extra rooms, and remote buildings. The unit includes a mixing motor, heater, and fan. BioLet toilets are available from the manufacturer and from various composting toilet suppliers. EcoTech also offers a urine-diverting toilet to expand the capacity of a composting toilet system, construct a drying toilet, and to provide source denitrification of sewage waste.

* Carousel batch composting toilets from EcoTech include self-contained and under-floor models. Composting waste is kept separate from in-use toilet. Similar to the Norwegian Vera (TM). Prices: $2200. to $3400. U.S.

Clivus Multrum composting toilets have been around long enough to be famous. (The Clivus Multrum composting toilet was invented by the Swede Richard Lindstrom in 1938.) Toilet models include a central composting system design, a waterless design and a foam flush design. The foam flush model does not have to be directly over the composter. The low water system automatically adds water to the composter. Clivis describes an integrated outbuilding restroom design too. The company offers factory technician maintenance service for the composter (which appears larger than some competing units, but CM may have other smaller models). This system uses a lower-temperature decomposition process known as moldering, which takes place slowly over several years and for this reason involves a comparatively large composting unit, manual liquid removal, and steps to address persistent pathogens or pests that may develop in the composter. Prices: $2500 - $5000. Clivus Multrum offers other wastewater disposal systems and products such as a greywater system which we discuss at our greywater information article.

CTS - Composting Toilet Systems six models, large below-toilet composter, built-to-order using fiberglass and plywood. Website does not quote prices. CTS also distributes Sun-Mar. Compost Toilet Prices $4600. to $5300. plus additional charges for support kit, solar-operated vents, fire suppression system.

Eco Toilets (New Zealand) Composting toilets for permanent dwellings as well as for holiday homes. Flushable Toilets, Non-flushable Toilets - Composting and Electric Toilets. EcoToilets Toatrone (shown here) is a non-flush waterless toilet which also performs urine separation. The composting reservoir is placed directly below the toilet. EcoToilets informs us that this composting toilet design is derived from the earlier Clivus Multrum composting toilet design. In this Eco Toilets composting model, a special "air staircase" allows air to penetrate through the composting sewage waste from below, a detail which the designer says makes the process of decomposition very efficient. Usage level: designed for permanent living. A normal household would remove waste as compost once a year. Eco Toilets also offers Aquatron flush composting toilets which use urine separation, flushing, and a composting container. Eco Toilets is located in Hamilton, New Zealand

Eco John EcoJohn Basic - A waterless separating composting toilet, which is perfect where an ecologically sensitive toilet facility is desired. Few product details were at the Eco John toilet website. This is a California company not the New Zealand listing just above.

• Eco-San, low density polyethylene, waterless urinal, wind-turbine vent system, outside composter attached to the toilet. Composting toilet price $3000.

Envirolet provides low water and no-water composting toilets. The company offers self-contained models and both low-water and waterless models using a remote composting unit. A 12V DC battery model is available as well. Prices for the Envirolet composting toilet line range from $1200 to about $2000. U.S. We're thinking of trying this model in a remote cabin in Northern Minnesota - watch this space for further comments.

LetsgoGreen is not a toilet manufacturer but rather a Canadian supplier of SunMar and other electric and non-electric versions of composting toilets (Ontario, Canada). The toilet shown here is the Centrex 2000 A/F central-flush waterless air flow composting toilet which uses a below-floor composting drum (110V, Composting Capacity: 4-6 Residential, 6-8 Weekend/Vacation Use, cost $1,795.00). Other self-contained composting toilet models are available.

Nature's Head is a U.S. made stainless-steel composting toilet, designed originally for the marine environment (use on boats). This is a portable, self contained, urine separating dry toilet that can be used where electricity is not available. The liquid waste compartment can store 2.2 U.S. gal. which the manufacturer recommends disposing of in a public restroom. Liquid urine waste is automatically separated from the solids. Solid waste that has composted (decomposed) for 3 months or more can be used as plant fertilizer; solid waste that has not composted that long can be bagged and disposed-of in a dumpster. The base product cost is about $850.00 U.S. The manufacturer notes that the toilet system does not produce the odors associated with holding tank toilet systems. It is suitable for cabins, cabanas, boat houses, hunting camps, RVs, basements, semi-trucks, and even pick-up trucks. The unit is vented to outside a venting kit chosen depending on the installation requirements. A 12-V fan is used to operate the ventilation system, powered by battery or a solar vent with backup solar-charged battery pack.The composting system is primed with damp, crumbly peat moss. Telephone: 251-295-3043 email: Sales@NaturesHead.net

• Nature-Loo composting toilet is an Australian product includes ceramic and plastic models
  
  
• Phoenix Composting Toilet from Advanced Composting Systems (Montana), requires 5 watts of electric power. Hand pump to remove excess liquid; rotating tines to move compost to the removal area. DC fan; can run on photovoltaics. Composting Toilet Prices: $4100. to $6100.

* SunMar provides low water and no-water composting toilets, and stand alone toilets as well as equipment to provide central composting supporting multiple toilets. (Their website says there are 20 models of low water or no water toilets.) SunMar uses a rotating drum to mix the compost. Sun-Mar is described by some vendors as not a true composting toilet but as a "dry toilet", smaller than true composting toilets, and using supplemental heat, air, and mixing to assure waste decomposition. Waste is kept on an outside compost pile for six months before spreading on soils. More frequent emptying and smaller capacity than "true composters" this toilet may be a best fit for a low-use remote cabin. SunMar offers a variety of composting toilets including a self-contained composting marine toilet model, the SunMar Mobile, certified by the U.S. Coast Guard ($1,489.00). Shown here is the SunMar Excel ne composting toilet [Click image for larger photo]. SunMar composting toilets are described below.

• Contact Us to list your product or service here - if you are a manufacturer of composting toilets or other alternative wastewater treatment system equipment your product may be listed at no fee. Website content critique, additions, and suggestions are also invited.

* - units that were recommended by RealGoods and which look good to us.

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TOILET ALTERNATIVES
    General Categories of Waterless
    Chemical Toilets
    Composting Toilets
    Greywater Septic Systems
    Holding Tank Septic Systems
    Incinerator Toilet Systems

More Reading about Composting Toilets and Septic System Alternatives

Products - for Alternative Septic System Designs
Buy Books on Composting Toilets
The Humanure Handbook discusses the recycling and composting of human waste.
The Composting Toilet System Book from Ecological Engineering - also available from Amazon.com
Real Goods article on composting toilets
Real Goods distributes several brands of composting toilets and offers well-informed articles about composting toilet features and alternatives.
Comparing Toilets a brief comparison of Composting, Low-flow, Incinerating, and Chemical Portable toilets from the National Small Flows Clearinghouse

• Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06
• Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com 11/06
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. 11/29/06
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