The Top Composting Toilet Designs

One of the most unsustainable aspects of our current civilization is related to how we deal with our own waste. For thousands of years, agrarian civilizations have understood that the fertility that one takes from the land in the form of crops, must be returned to the land in a similar manner. Both animal and human wastes have been used by indigenous and peasant cultures to maintain the sacred balance of fertility that ensures future abundance.

In the Mayan Highlands of Guatemala, small farmers raise herds of goats and sheep on communal pasture land, not so much for their meat, milk, or wool, but rather to harvest their poop as a fertilizer source for the bean and corn fields that sustain their families. In China, the infamous “night soil”, which was nothing more than human feces carted from the cities into the rural areas, was placed on top of rice fields (at night, to help avoid the initial smell) in order to maintain the long term fertility of the fields that provided, year in and year out, the most important food staple of most Asian cultures.

Today, however, most of us have no idea where our waste goes once we flush it down the toilet. If the municipal sewer system were to become non-functioning, many people would have no idea what to do when Mother Nature comes calling. We´ve become so accustomed to indoor plumbing and flush toilets, that if some sort of catastrophe were to occur, millions of people would be incapable of dealing with the most basic hygienic practice of getting rid of feces.

Problems with Flush Toilets

Defecating in precious drinking water isn´t exactly a smart idea. Besides losing billions of gallons of water each year, pooping in water is akin to throwing money down the drain. Human urine and feces could provide needed nutrients for small farmers if correctly composted, thus helping farmers to lessen their dependence on unsustainable, oil-based fertilizers that cause damage to the soil food web.

Furthermore, flush toilets can cause hygienic problems as anyone who has had to deal with a stressed septic tank will know. Putting feces and urine into water or burying it under ten feet of dirt leads to anaerobic decomposition conditions. Anaerobic decomposition doesn´t only stink to high heaven, but it is also a breeding ground for a number of dangerous pathogens.

The Use of Composting Toilets

Composting toilets have been around for hundreds of years. As we mentioned above, the Chinese have been using human waste to maintain the fertility of their fields for thousands of years. Today, there are dozens of models for quality composting toilets that are safe and sanitary. The basic idea is to combine our waste which is of high nitrogen content with some sort of brown organic material that has high carbon content. The combination of high nitrogen and high carbon content (ideally attempting to shoot for 80% carbon and 20% nitrogen) leads to aerobic decomposition that is healthy, safe and leads to quality humus. Dried leaves, sawdust, or chopped up hay bales make great brown material for a composting toilet system.

When our high nitrogen waste is mixed with the high carbon content of brown organic material, thermophilic composting ensues. Thermophilic simply means that as microorganisms begin to break down the material, temperatures higher than 160 degrees Fahrenheit are achieved. This temperature ensures that all harmful pathogens will be killed off leaving a dark, fertile soil that can be used safely to fertilize fruit trees or flower beds.

Different Composting Toilet Designs

While there are now several different commercial composting toilet designs on the market today, you can also easily construct your own composting toilet to save on expenses and design a system that is best for your situation. The simplest composting toilet system is to simply go to the bathroom in a five-gallon bucket and cover your waste with a handful of brown organic material after each use. Once the bucket is filled up, you can take it to a compost bin where you again cover the material with an extra layer of brown material. This “humanure” system is used by thousands of people worldwide and offers an easy, simple, and efficient way to deal with your waste. After several months of decomposing in the compost pile, your “humanure” will be safe to use as a fertilizer for fruit trees or flower beds.

If the idea of having to move your waste on a weekly basis isn´t appealing to you, building a larger two compartment composting toilet system is another option. Cinder blocks are used to build a fairly large compartment or “tank” that is divided into two sections. On top of the tank, two toilets are installed. One of the toilets is sealed off while the first section of the tank is slowly filled up. After each “use”, you´ll need to deposit a couple of handfuls of brown organic material in the same way as with the bucket system.

Once the first compartment is filled up (usually between six and twelve months), it is sealed off and the second toilet is used. By the time the second compartment is filled, the first compartment will have composted down into an odorless, fertile black soil that can be removed from a small door left at the bottom of the tank and used on fruit trees or flower gardens. You switch back and forth between the two compartments as they fill up over time.

Through the use of a composting toilet system, you will minimize the amount of potable water your family uses thus allowing it to be destined for other purposes. At the same time, you will be safely and hygienically getting rid of the potential pathogens associated with human waste and creating fertile compost for your agricultural use.

Tobias Roberts

After working in the development industry for over a decade, Tobias decided it was time to stop advising Central American farmers how to do things if he didn´t have a piece of land to live coherently with what he taught. Together with his family he runs a small agro-forestry farm, tourism cooperative, and natural building collective in the mountains of El Salvador.


  1. If your sewers broke, and you HAD to do this, this is enough that you would figure it out within a few days. Having done this myself, I would recommend wood shavings over sawdust. Sawdust cimpacts too much.

  2. This type of compost toilet reminds me of the ones Queensland towns had back in the 1940’s and 1950’s. The old outhouse up the back yard with it’s sawdust bin beside the wooden toilet with the newspaper cut up in squares with string threaded through them and hung up on the wall. The wonderful council man that took the waste away each week. Mum always made sure there was a Christmas gift left out for him each year. We were all very healthy back then so I can see nothing wrong with this concept.

  3. Agreed, as above – I read this to check out some designs and didn’t find more than themost basic bucket model. Even the 2 bay system as described doesn’t mention the need for good air flow and fly-proofing that makes these toilets amenable to the general public (including your friends!) Also agreed with comment that wood shavings are better than sawdust, as allows more air flow. Coarse leaves have same effect. A review of composting toilet designs, including commercial and home built models, would be appreciated.

  4. A comment:
    A common misconception with composting toilets is the idea that thermophilic breakdown occurs in a chamber. This is simply false in a system that gets added to everyday. In no way can these temperatures be created or sustained to cause die off of pathogenic bacteria. Only if human poo is composted in a big heap all at once with the right balance of browns and greens (not just wood chip but also less dense carbon like grass clippings) will these temperatures be reached . In most systems, it is time, worms and microorganisms that lower the e coli count.
    I am not a fan of the chamber system described in the article. The author has not mentioned the method for removing or dealing with urine. If the system described puts the urine in chamber with the poo either the ‘compost’ becomes too wet and anerobic or problems occur with piping out the black liquid.
    I recommend a wheelie bin to compost in with a false floor to drain any excess liquid or better- a urine separator to reuse the urine.
    My 2 cents anyway!

  5. Good points made in the previous posts. A few little design features make a composting toilet function much better (and also make it much better received):

    Insect and rodent-proof compost chambers, with moisture barriers (e.g., polyethylene) to prevent seepage into groundwater, or vice versa.

    A ventilation stack to lift any odors up away from people (probably the least important on this list).

    A urine funnel and separate storage, and convenient system of flushing the hose between the two with water to prevent salts from clogging hose (only takes a very small amount of water).

    Smart chamber and chamber-door design, so climbing inside the chamber is not necessary for cleaning out finished compost (or specialized long handled shovels).

    Excellent drainage, and flood and rain-proofing, as well as protection against rising damp, etc. It is a good idea to build a compost toilet as if you were building to resist the most humid, rainy climate – since they contain a pile of moisture and decomposition-accelerating nutrients, and you also really don’t want them to fill with water during a flood (see resources on natural building for ideas for affordable, easy, effective and beautiful construction strategies using natural materials).

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