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Wednesday, April 27, 2005
Composting Toilets

Composting Toilets 101

We thought we would add some basic inforation about composting toilet systems. This is taken from Composting Toilet World and provides some very insightful info on compost toilets. It is a great read for those brand new to the concept of composting toilets.

Composting Toilet World is an advocate for the the use of composting toilets worldwide.

Composting Toilets Explained
Source: Composting Toilet World

Many people now know about composting toilets, particularly those in the alternative movement who are quite familiar with composting in their gardens, and who understand the advantages of recycling and simplification of our needs.

But to the many others who have not really thought about where their sewage goes after flushing, the thought of composting your own wastes is a little uncomfortable. Objectionable questions are fired at you when you first introduce the concept to someone, and many persons leave the subject still thinking that a composting toilets is a old pit toilet, remembered unpleasantly from camping trips.

Well, composting toilets are far from being pit toilets! They range from simple twin chamber designs through to advanced systems with rotating tynes, temperature and moisture probes and electronic control systems.

They are effective biological converters of human and household “wastes”, saving money and energy for the person and community and starting the regeneration of the planets environment that is long overdue.

This will give you a basic introduction.


Composting toilets are toilet systems which treat human waste by composting and dehydration to produce a useable end-product that is a valuable soil additive.

They come in a variety of models and brand names as well as different shapes and designs to enhance the natural composting process.

They use little or no water, are not connected to expensive sewage systems, cause no environmental damage and produce a valuable resource for gardening.

The systems can be broadly divided into two different types:

With the batch systems, a container is filled and then replaced with an empty container. The composting process is completed inside the sealed container. The system may have a single, replaceable container. Or it may be a carousel system where 3 or 4 containers are mounted on a carousel and a new container is spun into the toilet area when the other is full. After a full cycle is complete, the first container is fully composted and ready for emptying.

These systems are in a constant state of composting. “Deposits” are put into the system, composting reduces the volume and moves it downward where it is harvested after 6-12 months as fully composted material.

All systems are designed to treat the “deposits” by composting, worm processing, micro and macro - organism breakdown, and by dehydration and evaporation of moisture.

There are a wide variety of systems including:

  • Manufactured home or cottage use systems. (Like Envirolet®!)
  • Manufactured, large tank, inclined base models suitable for heavy loadings.
  • Owner-built, two chamber mouldering systems that are basic, but effective.
  • Owner-built from concrete blocks and concrete inclined base. Constructed in with the house foundations.
  • Wide variety of small units which fit into existing bathrooms. Many have dehydration fans and heaters.
  • Vacuum flush unit for production of worm castings.
  • Full flush systems with centrifugal action to deposit wastes into composting chamber.

New technologies and products, as well as over 30 years experience is now setting the scene for a major expansion of composting toilets throughout the world.


Besides pit toilets, present toilet systems are either “sewered systems” or on-site “septic or mini-treatment systems”. Both are based on the principle of using water to transfer the “wastes” to a treatment system. Whether this is a septic tank just outside the house, or a sewage treatment plant 10 miles away, both must treat a large volume of raw effluent.

This historical use of water to “cleanse” away the toilet wastes is where the first problem occurs.

Raw sewage starts to break down by a process that utilises oxygen within the water.

Once this oxygen has been used up, the breakdown of sewage is changed to microorganisms that perform anaerobic (non-oxygen) respiration.

The byproducts of anaerobic respiration are nutrient-rich effluent and flammable methane and other foul smelling gases. This is the traditional smell associated with septic tanks and sewage treatment plants.

In many cases around the world, untreated effluent is left to run down natural streams and rivers into lakes and oceans. The high nutrient value of the effluent causes algal blooms in these waterways, which as they die and are decomposed by microbes which use up the dissolved oxygen in the water. This in turn reduces dissolved oxygen levels which kills marine animals. The effects can be quite devastating up the marine food chain.

The production of effluent brings us to our second major problem. This is the mixing of industrial and agricultural effluents with human effluent.

Human effluent could be treated and reused as agricultural sludge and liquid fertiliser, but the addition of toxic byproducts from industry produces questionable quality effluents and sludge’s. This wastes valuable nutrient resources.

A third problem is associated with these nutrient “Resources”. There is a massive nutrient leak occurring at present in our societies. Fertiliser nutrients are mined from fossil and guano reserves and manufactured into fertilisers which are applied on agricultural lands. From here it leaks in two ways.

First, unused fertilisers run down into streams and river and are lost into lakes and oceans.

Second, food crops and animal farming takes nutrients away as farm products. These are transferred to us as the food we eat. From there they become sewage wastes and ultimately end up causing pollution in lakes and oceans. In the future, we will find that are reserves of natural fertilisers will diminish, and we have to start recycling the nutrients that we have in the systems at present.

The waste of another natural resource, clean water, is our fourth problem. Building expensive dams, piping water hundreds of miles, treating it with expensive processes, and then using 40% of this treated water to flush away a small quantity of human byproducts is utter madness.

The massive costs of infrastructures such as dams and sewage systems is causing financial burdens for many families, particularly in cities, where the money would be better spent on solving social problems.

Overall, the present system of treating “humanure” is a wasteful and expensive burden on our communities and the environment. To reverse this system, and build a sustainable systems of “waste” re-utilisation is possible using systems such as composting toilets.


The advantages of natural waste treatment systems are many and varied. The following section shows the benefits of the system in comparison to existing waterborne waste treatment systems. These benefits improve conditions for the individual, the community and the environment. An understanding of how your system benefits the individual and the community will help you to maintain it and confidently explain it to others.


Water Use Reduction (20 -50%) A significant savings in water storage will result if the household is not on reticulated water supply. Combine this with wastewater re-utilisation in irrigation and other household water reduction techniques and water storage costs can be cut by up to 60%.

Shock Loading Capacity Loading shock for large gatherings is achieved easily with correctly sized composting toilet systems.

Odor Problems Reduced The suction air flow in most composting toilets takes toilet and bathroom odor out of the room and acts like a constant extraction fan.

Lower Household Maintenance Costs Sewage rates and water rates (metered) can be in the order of $500 per year, a significant cost. This will only increase if the demand for sewage system upgrading increases. Other on-site systems have annual maintenance costs that are obligatory. Local authorities will be increasingly paying rebates to households who own composting toilets.

End Product Recycled While only small in amount, the solid end product is a valuable humic fertiliser that can be utilised around trees and gardens.

Reduced Greywater Loading Where composting toilets are installed instead of septic and mini-treatment systems, there is a large reduction in the “loading” on the effluent treatment system by the removal of “blackwater”. Smaller, less maintenance, greywater systems are possible.

Independence A household with a composting system is independent from potential problems of the waterborne sewage system. If future water shortage or system backup problems occur with conventional systems, there is not much that you can do personally about it. On-site composting systems are much more flexible, they are easier to fix and have less damage potential if operated incorrectly.

Recycling The composting toilet possesses the ability to recycle much of your household waste. Food scraps, paper, lawn clippings and grease from you grease traps and greywater systems can be composted back through the toilet. If you choose to put in a reed bed greywater systems, the annual clippings can also be composted. There is no wastage in this system.

Unusual Sites Composting toilets can be installed in many different situations which would not accommodate other systems. Rocky sites, high water table, no water storage, environmentally sensitive, close to running watercourses, and swampy ground. All these difficult site situations can be accommodated with a small amount of alteration to the basic system design.

Together with the personal benefits of the composting toilet there are overall benefits to the society and the environment.


Water Use A reduction in water use allows the large capital costs of dams and reservoirs to be spread over a greater population. It also enables decentralised water sources to be used.

Reduced Marine Pollution Nutrient load on streams and rivers is almost negligible. This results in more oxygen being available in the water and a return to improved activity of marine life.

Pollution Detected Quickly Without sewage systems to flush away wastes, It would be easier to ascertain where toxic wastes are being leaked into watercourses. Industry would be more willing to rectify these problems if it were easier to identify the sources.

Damage limited Miscalculation in individual composting systems has a much smaller impact than the same mistake in a large centralised system. It is also easier to rectify and return to normal operation.

Flexibility of Planning Composting toilet systems are built only when the need arises. The high headwork and treatment costs of conventional sewage systems must be borne by the community ahead of development. If development does not go as planned, then money is wasted.

Less Environmental Impact Compared to sewage systems, on-site composting and greywater treatment has less impact on the environment; * Large effluent releases into watercourses and oceans are avoided. * Disruption to soils systems through pipeline installation is eliminated. * Leakage of raw sewage into groundwater through pipe deterioration and breakage is eliminated.

Flexibility in Estate Planning By eliminating the planning constraints of the sewage system underground piping and infrastructure, housing developments can be designed with more emphasis on environmental and social considerations, rather than how best to situate the blocks to make pipes run straighter.

For such a simple technology, the benefits to the individual and to the community are quite amazing!

Courtesy of Composting Toilet World.