Composting Toilets 101

What is a composting toilet?

Composting toilets use urine diversion and the natural processes of decomposition and evaporation to breakdown and reduce the volume of human waste, transforming it into a soil-like compost material. The decomposition/composting and evaporation process can be thought of as what happens to a banana peel when left out in the open. It starts out yellow, moist and smelling like a banana with a relatively thick skin – after a few days it becomes a black, shriveled up, odor-less, dried out fraction of itself. That is decomposition/composting at work. Waste entering the toilets is over 90% water, which is evaporated and carried back to the atmosphere through the vent system. The urine diversion system carries sterile urine to storage containers to be diluted and used as fertilizer or discharged directly into the ground via a shallow soak pit.

The natural decomposition process, which is essentially the same as in your standard backyard garden composter, is enhanced in waterless composting toilets by manipulating the environment in the composting chamber.

The correct balance between oxygen, moisture, heat and organic material is needed to ensure a rich environment for the aerobic bacteria that decompose the waste. This ensures odor-free operation and complete decomposition of waste.

When human waste is properly composted, levels of pathogens or viruses in the waste are dramatically reduced. The pathogens and viruses are destroyed by bacterial breakdown and desiccation (drying out).

As an added measure to address potential odor or vector (fly) issues, Toilets for People recommends the addition of a small amount of wood ash or charcoal ash or agricultural lime immediately on top of the waste before the addition of bulking material. In addition to neutralizing any odors and serving as a natural pesticide for vectors, the addition of caustic ash/lime will raise the pH of the waste – further destroying the pathogens and viruses that thrive in an acidic environment.

It is recommended that the soil-like compost material coming out of a composting toilet be buried nearby with an ash/lime cover as a final disinfectant. Under certain circumstances, it can be used as a nutrient-rich fertilizer for growing trees. However it is not recommended for surface crops or ornamentals since there is the possibility that some pathogens remain in the waste, which can be harmful if exposed to. As long as the compost is in the ground, then the exposure route is not present.

The TfP Waterless Toilet optimizes the composting process by having a two-chamber system.

Chamber 1: The Rotating Drum
It starts with a horizontally mounted rotating drum, much like a garden composter, that sits inside a box. This proven technology has been the industry standard since the 1970s in the US and Canada.

The first chamber is the rotating drum. Inside this rotating-drum rapid, active composting of the waste and toilet paper takes place under aerated and moist, but not wet, conditions.

The urine diversion system separates this sterile liquid waste and from the pathogen-rich solid waste and is generally discharged into a soak pit. Soak pits for this purpose are typically rock filled holes approximately 1 foot deep and 1 foot in diameter. Draining away leachate ensures optimum moisture levels are maintained while keeping the waste in the drum from going anaerobic which can cause odors.

In addition to maintaining aerobic conditions to minimize odors, the TfP Waterless Toilet also employs a ventilation system to keep the unit under negative pressure and therefore odor-free.

The rotating drum is the ideal way to compost waste since it offers operational simplicity, and an environment where there is warmth, moisture, organic material, and oxygen. Within this environment, aerobic microbes flourish and work much more quickly to break down waste and convert it back to earth.

Advantages of the Rotating Drum
Ease of Emptying– When the drum gets to be around ½ full, you pull out the ½” metal drum locker rod from it’s hold in the step and rotate the same handle clockwise for one rotation of the drum to empty. Then you leave the compost in the drawer for a month to cure, or if you are emptying after leaving it all winter, take it right out. There is no digging, poking, chiseling, or handling of fresh waste.

Ease of Mixing – In order to mix the compost, you turn a handle, which turns the drum. Nothing can stick or break. No complicated gear system. This ensures ease of mixing.

Supplying Oxygen – the rotating drum design is the easiest and best possible way to thoroughly and completely mix and oxygenate the whole compost. Rotate the drum, and the entire compost pile is tumbled and infused with oxygen. Oxygen is one key ingredient that allows aerobic bacteria to break down waste quickly and without odor.

Controlling Moisture – compost must be kept moist but not saturated. Moisture control, the other basic requirement for good composting, is one of the outstanding benefits offered only by the rotating drum. Below 40% moisture content, composting slows and eventually stops completely. The tumbling action during periodic mixing distributes moisture evenly throughout the compost. At above 60% moisture content, liquid starts to drive out the oxygen in the compost, and the compost becomes increasingly anaerobic – like a septic system. The drum system optimizes composting by distributing excess liquid from wet areas to dry areas.

Maintaining Warmth
– The microbes generate their own heat as they work. This warmth is held in the compost by the mass of material inside the drum.

Aerobic Bacteria Ensure Odor-free Operation
– Uneven distribution of oxygen and moisture allows anaerobic bacteria to take over. These microbes produce bad odors and do not allow the waste to break down quickly. The superior oxygenation and moisture control provided by the rotating drum provides the ideal environment for aerobic bacteria to odorlessly break down organic material. They quickly convert organic material into water and carbon dioxide.

Chamber 2: The Plastic Bin Finishing Drawer
The second chamber is the plastic container, which catches and passively composts and cures the waste coming out of the rotating drum. This second chamber, which is essentially a durable but affordable bus-boy bin that you would see in a restaurant, ensures that the finished compost is not only contained but also, since it has handles on either end, is easy and safe to remove and transport.

Advantages of a Separate Plastic Bin Finishing Drawer for Compost

Complete composting – The degradation process can be completed in the drawer without contamination by fresh waste.

Drying out – Compost in the drawer is gradually dried by airflow until ready for removal. This drying out (desiccation) further reduces pathogens and odors.

Easy removal – Finished compost can be simply and safely removed using an easily-accessible isolated container. The pull out finishing drawer is removed by hand (no tools or screws are needed). The compost may be emptied whenever more compost is to be extracted from the drum. For seasonal units, several drawers may be removed in the Spring, reducing the compost level in the drum to 2-4″ to make room for next year’s operation.

Simple to Use, Operate and Maintain the TfP Waterless Toilet

You either sit on the toilet seat or squat on top of the larger size TfP Waterless Toilet, pee and poop into the drum, cover it with saw dust or dry leaves or ash, spin it once a week. Natural aerobic decomposition eliminates dangerous pathogens and foul odors. It also reduces the volume of the waste by 80% so the user only needs to empty the drum out once every 2 months.

Waste, bulking material (saw dust, dry leaves, etc) and small amounts of ash/lime enter through the waste inlet port at the top of the drum. Toilet paper and feminine hygiene products are to be placed in a separate waste bin and not in the waterless toilet. To mix and aerate, rotate the drum counter-clockwise periodically (at least 3 full revolutions once per week), simply by turning the handle on the front of the TfP Waterless Toilet. During counter-clockwise rotation the inlet door closes automatically keeping the compost in the drum. After rotating, lock down the drum by inserting the ½” metal rod into the ½” hole in the step in a top dead-centered position ready to receive new material.

To empty compost from the drum simply rotate the drum clockwise. Now, the inlet port in the drum opens automatically and compost drops directly into the compost-finishing drawer.

After you empty it out, you dig a hole a foot deep, put the compost in the hole, cover it with wood/charcoal ash or agricultural lime (this is to dry it out and raise the pH which kills the pathogens thereby disinfecting the waste) and finally cover it all over with dirt and you’re done!

The compost can also be used as fertilizer for planting trees seedlings for cash crops or reforestation efforts – as long as it is buried with ash/lime a foot deep under ground below the tree root ball.

The compost is not to be used to fertilize surface crops in case any pathogens are still present in the waste.

Ventilation to Ensure Odor-Free Composting Toilets

This is hard to get your head around unless you are physically standing in the room with a properly functioning composting toilet. Our conception is that toilets human waste treatment systems smell bad – however, we are accustomed to anaerobic septic systems, which do smell bad. However, due to aerobic composting and constant negative pressure inside the TfP Waterless Toilet, our toilets don’t smell.

Compost must be mismanaged significantly or venting installed incorrectly in order for it not to operate odor-free. The only area where you may have a problem is on the outside, at the very top of the vent stack. For instance, if the vent discharges at a level where people in another structure are living on an upper floor. This is an un-usual case, but if it becomes an issue a filter box to absorb the odors can solve it. Otherwise, any odors at the end of the vent are carried into the air, and do not blow back onto the property.

If you only need to place to pee – Consider the TfP Female Urination Fixture or TfP Urinal

If you only need a place to pee, use the TfP Female Urination Fixture (sit down or squat versions available) for women or the TfP Urinal (for men, stand up style).

The urine is captured by these units and channeled into a tube that runs to a soak pit underground. Urine is essentially a sterile liquid, as sterile as tap water, and therefore can be discharged directly without treatment.

The TfP Waterless Toilet is designed to divert urine from the drum which is meant to treat solid waste. If TfP did not employ the urine diversion system, the compost would become wet and saturated, reducing aeration and slowing down the composting process. The compost may even go anaerobic and odors may become an issue. By using the urine diversion system, the functionality of the TfP Waterless Toilet is optimized since it does not have to treat a large amount of liquid waste, which it was not designed for.

Customer Service
Toilets for People is here to help, both in the sales process and after-sales service. We are committed to working with any TfP Waterless Toilet, TfP Female Urination Fixture or TfP Male Urinal owner who has a problem until the problem is solved. We understand that unfamiliar technology can lead to questions and we are always available to provide answers.

For more general information about composting toilets, history and applications check out: