So, like so many these days, you’re looking into composting as a way to reduce your carbon footprint. Naturally, you came across compost toilets and had a pretty reasonable question.

How does a composting toilet work?

composting toilet
Earth 911

Well, they work via natural processes and a little man-made ingenuity without giving away the grand finale. Keep reading to gain an in-depth understanding of how compost toilets work.

Composting Toilets 101

Composting Toilets 101
The Spruce

It’s all about two processes here: decomposition and evaporation. Did you know that human waste consists of 90% water? That means that most of your bowel movements will just evaporate through the vent of your composting toilet if provided the right environment. What remains looks like garden variety soil (which is why so many people get the two confused).

What you’re left with is safe to use, thanks to the bacterial breakdown and removal of parasites that occur during decomposition. Now, there’s more that goes into the design and maintenance of a proper compost toilet, but now you have the basic idea.

Usable Compost is the Best Compost

So, now that we understand the basics of how a composting toilet works, we can go about discussing design techniques that optimize evaporation and decomposition. We also want to be sure that our design outputs compost safe for use.

Compost Toilet Design

composting toilet design chambers
Lets Go Green

A well designed composting toilet successfully does three things:

  1. Composts waste and toilet paper efficiently and without unreasonable odor – Did you know that Port-a-Potties and their pungent blue liquid do nothing to sanitize waste? If you’re going to use the product of your compost toilet on your yard and garden, then you’re going need it to be safe. If you aren’t going to use it for this purpose, then how can the toilet be efficiently pumped? Also, you don’t want it stinking up your home.
  2. Allows for the evaporation of liquid waste – If the environment in your compost toilet doesn’t allow for the liquid to evaporate, then you’ll never have usable compost.
  3. Outputs compost that is safe to use – Your stomach primarily contains things that aid in the breakdown of food and die shortly after leaving the body. But, what about those microbes that can survive on the outside? Killing these are the key to a usable compost toilet, and the answer is heat.

You can probably guess that a modular design is going to work best for composting toilets as you want to separate the different parts of the process.

Composting Waste & Toilet Paper Without Odor

A common issue with alternative toilets is their odor. Whether a porta-potty at an NFL game or a vault toilet at a National Park, if you know what I’m talking about, then you know what I’m talking about.

While you probably assume that the smell comes from the feces, you may be surprised to hear that it emanates from the urine – a result of the high ammonia concentrations within. The ammonia is also inhospitable to the microbes in human feces that aid in the breakdown. As a result, mixing feces and urine is an ineffective way to cultivate safe compost.

So, to have an adequate compost toilet, you’ll need a solution. Fortunately, newer composting toilets feature designs that separate the two kinds of waste. There is some scholarship that argues that if you use your compost toilet the allotted amount, then these problems won’t exist. At the same time, you don’t want to be ready to spread your compost on your garden only to find out that it’s toxic.

An additive or bulking agent such as sawdust or peat mix will help the breakdown processes, alleviate some odor, and ensure that your compost is safe to use.

Evaporation of the Liquids

If you’re using a compost toilet featuring a chamber design, then this bit should happen naturally. Some good options for toilets with this design include Ecodomeo and ToiletTech.

You may also look for an option with a heating element as this will speed up the evaporation process. Be careful though, as you don’t want your compost to lose all its moisture.

Just for reference, urine is approximately 95% water, and fecal matter is around 75%.

Outputs Safe Compost That’s Usable

To get safe compost, you’ll need to do a bit of thinking before purchasing and installing your composting toilet.

  • How many people will use the compost toilet?
  • What’s my climate like? How will it effect the processes going on in the compost toilet?
  • How frequently would I like to empty my compost toilet? Am I willing to do any maintenence?

The more people using your toilet, the faster it’s going to fill up. Filling your compost toilet too quickly doesn’t allow the natural processes enough time to finish. It’s pretty easy to see where I’m going with this. As long as you aren’t hosting weekly fiber-heavy dinner parties, you should be okay.

Did you know that in extremely cold climates (specifically at high altitudes), the waste won’t get hot enough to decompose? As a result, a compost toilet is a difficult thing to have in the cold. You can mitigate these climate concerns by keeping your outhouse warm.

In an ideal world, you would only have to deal with the gross part of your compost toilet annually. In reality, however, there’s a bit more maintenance that goes into keeping your eco-friendly lue operational.

Depending on the model you choose, there can be a need to dry, empty, or turn the compost occasionally. While this can seem like a hassle, if you’re living off the grid, you won’t want to waste resources on disposing of waste. A composting toilet is an excellent option for those in this predicament and has the added advantage of giving back by way of organic fertilizer.

How does a composting toilet work in a tiny house?

tiny house composting toilet
Tiny House Giant Journey

Are you thinking about installing a compost toilet in a tiny home? Well, it’s doable and pretty similar to if you were installing one at a standard size house. The only difference in the tiny house is the need for a slightly smaller toilet.

If you want to use the compost in your garden, though, then you’ll want to go as big as you can. The larger the chambers of the compost toilet, the more time is given to our two essential processes – evaporation and decomposition.

How does an RV composting toilet work?

RV composting toilet
Tin Can Creative

Are you considering a composting toilet for an Airstream? It’s a pretty awesome way to live if you do it correctly. A water closet on wheels that also composts though is a reasonably tough ask.

The reason – lack of time. In a small space like an RV, you’re going to need a space-efficient composting toilet. As a result, the chambers of the toilet aren’t as large and fill quickly. Because the chambers are filling so fast, the decomposition doesn’t have enough time to finish resulting – possibly – in some nasty microbes not ideal for fertilizing your fruits and veggies.

While installing a compost toilet in an RV is still a tremendous eco-friendly step that you can take, it may not tick all of the boxes you think it will.

If you’re camping with your compost toilet on wheels, then you can use the campsites hookups to dispose of the urine. If you’re way off the grid, you can dump and bury your waste; just be sure you’re well away from water and public paths.