What is a Composting Toilet?

Written by Rob Guros in Uncategorized

The need for alternative sanitation systems is a reality in many cities of the globe. With most of the cities relying on water treatment plants to process human waste, these complex processes are not rapid enough to quickly process the large amounts of human waste so that it does not overflow into water bodies in the rainy season. Composting toilets are among the innovations directed towards resolving this situation. 

What is a Composting Toilet?

A composting toilet is a dry toilet that uses aerobic decomposers to break down human waste and convert it to a passive nitrogen-rich material that’s similar to humus (the organic component of soil). 

Aerobic decomposers are organisms that work in an oxygen-rich environment to break down the waste, which explains why these toilets are sometimes called biological toilets. However, the efficiency of these toilets has often been met with doubt, with many potential users harboring questions about their nature, function, and hygienic standards.

This article is meant for those looking for answers about composting toilets. It will address questions on what a composting toilet is, how it works, and a few other frequently asked questions. 

Why Use Composting Toilets?

Human waste disposal is an essential service for healthy living. Currently, the flush toilet is most widely used, disposing human waste into sewerage systems for treatment and proper disposal. 

But in the world today, large urban populations often put a strain on the sewage systems of their cities. In some rural setups, sewage systems are altogether missing for large populations. 

The WHO estimates that 2 billion people do not have basic sanitation facilities such as latrines and toilets, with many defecating behind bushes, in street gutters, or into water bodies. This situation not only creates a health hazard but also underscores the need for alternative ways to dispose of human feces. 

As such, people primarily use composting toilets as a cheaper and safe alternative for human waste disposal. Additional reasons include:

But how does a composting toilet work to achieve all these benefits? 

How a Composting Toilet Works

Composting toilets are generally categorized as self-contained (housing the composting system) or central/remote systems (directing solid waste to a remote centralized system). But you might also read about subtypes of composting toilets, including electric composting toilets, dry composting toilets, solar composting toilets, and portable composting toilets.

Irrespective of these types, composting systems work in the same manner. Let’s dive into the parts and working of a self-contained composting system below.

The parts of a self-contained composting system

The basic parts of a composting toilet include a compost chamber, a flush door, a liquid container, a flush handle, an agitator bar, a spider handle, a vent hose and fan, a mounting screw and in some cases a finished compost chamber.

How it works

The basic concept in composting toilets is that solids must be separated from liquids. In order to ensure proper composting, three conditions must be maintained:

  • Minimum moisture level to enhance the functioning of the aerobic bacteria.
  • A balanced carbon-nitrogen level that is maintained by keeping urine out of the chamber and adding carbon-rich material (peat moss, coconut fiber, and sawdust).
  • An optimal temperature range (60-100 degrees Fahrenheit) to keep the bacteria active. 

Assuming that your composting toilet is assembled, this is how you use it.

  1. Fill the composting chamber with the carbon material up to where the agitator bar is.
  2. When you use the toilet, rotate the spider bar twice or thrice to allow the agitator bar to mix the solid waste with the existing compost (the urine is directed to the liquid drain from the onset).
  3. When the urine bottle is full, unlatch it and remove it to safely dispose of the liquid.
  4. Empty the composting chamber of the solid waste and dispose of it properly according to the rules of your local area. Some composting toilets will send the processed humus to a separate finished compost chamber that can be emptied with ease.

Note that composting toilets will need electricity to power the fan.

When well maintained, quality composting toilets do not need any form of cleaning. Remnants of the composting matter are good for initiating decomposition with the next round. 

A spray bottle with water and a little vinegar can be used to clean any dirt particles sticking in the passage when the toilet is used. This helps to keep the passage clear and avoids any foul odors.

Other Frequently Asked Questions

The novelty and mystery that is associated with composting toilets elicit a few other questions. We address 4 of them below:

Does a composting toilet emit a foul smell?

Some simple models of composting toilets may emit foul odors. But well-designed models with good ventilation do not. The key here is good maintenance. This is done by keeping the passage clear and maintaining the right carbon-nitrogen balance and temperatures. If done properly, composting toilets should not emit any foul smell.

The most smell you should be able to detect from a composting toilet is an odor similar to mulch owing to the process of decomposition. But this is also rare considering that the whole system is usually encased. 

Does a composting toilet process urine?

A lot of people wonder whether they can pee into a composting toilet. As already stated, composting toilets work by separating solid and liquid waste. Even though some past models had both wastes disposed of into the same chamber, today’s models have the two wastes disposed of separately from the onset. This allows the right amount of moisture in the composting chamber, facilitating bacterial action.

But there is another reason urine should be kept out of the composting chamber. The urea in urine turns into ammonia, which is not only smelly but can kill the microbes. A study in 2013 discovered that high amounts of ammonia inhibit the efficiency of the aerobic decomposers.

Where and how often do you dump the waste?

The ‘where and how often you empty your composting toilet’ question is best answered with a “depends on the situation.” Let’s break that down for both the liquid and the solid wastes.

Liquid waste

We visit the toilet more times to pass urine than we do to defecate. We also send down more urine than excreta. That means the liquid bottle will fill up more often and can be emptied every couple of days, depending on the size of your container. Urine may also tend to smell if left around for too many days. 

One way to dispose of it is by mixing it with water and watering the grass outside your home. But don’t do that in one spot too often as to avoid feeding the grass with too much nitrogen. You may also send the urine to the greywater sewer system or tiny house greywater tank if you are connected to one from your shower. 

Solid waste

As stated earlier, composting chambers can go for weeks or months, depending on their size and how many people are using it. If you have a model rated for 90 uses and you are alone, that may go for up to 3 months. But if three people are using it, then it may require emptying after a month or less.

Cooler seasons may require you to empty your composting chamber more frequently. If the spider handle gets hard to turn, that’s also a sign it’s time to empty.

With solid waste, dumping greatly depends on zoning laws. Some states may allow proper disposal of the waste as compost in fruit or aesthetic gardens but not vegetable gardens. This is because bad bacteria in human feces are hard to die.

In states where composting toilets are legal, you might be able to empty the compost in biodegradable disposal bags and throw it in a dumpster.

Are there risks and drawbacks associated with the use of compost toilets?

Despite the earlier mentioned pros associated with composting toilets, there are some risks and drawbacks we should keep in mind. 

Human waste from composting toilets is not always fully processed, and even when it is processed, pathogenic bacteria and viruses can stay in the composting chambers and the humus. These may be a health threat if they find their way back to humans. 

The maintenance of composting toilets may be tedious when it comes to emptying the chamber and urine bottle as well as refilling the composting chamber with the carbon material. Having carbon materials readily available is also an additional headache.

Zoning rules around the use of composting toilets are still in the initial stages in most states. This leaves uncertainties in the use of these toilets. 

Conclusion

Composting toilets are biological toilets that use aerobic decomposers to process human excreta into humus.

Composting toilets can be self-contained or a centralized remote system. The self-contained system composts solid material that can be disposed of in gardens as humus or placed in biodegradable bags and disposed of in a dumpster. The urine can be mixed with water and used to water fruit and aesthetic gardens, but should not go to the composting chamber. 

Keeping a hygienic and odor-free environment with a composting toilet depends on how well you maintain it. This means ensuring the carbon-nitrogen balance and the right levels of moisture and temperature. 

Even though environmentally friendly and a possible remedy to the strained sewerage systems in most cities, composting toilets can harbor pathogens and should be handled with caution while practicing a high level of hygienic standards. 

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