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Lesson No. 1 (and No. 2)

"How Do Composting Toilets Work?" asks the savvy commode consumer. Out in Mother Nature's all-encompassing living room, animal or human waste would normally be broken down into soil-enriching humus through a combination of dehydration and aerobic decomposition (that means that it needs air, not leg warmers). It's all natural and it's worked for, well, forever. A composting toilet uses the same processes to deal with waste, leaving you with a minor bit of compost that can either be disposed of or used to enrich the soil in your garden or yard. Neat, right? And all without using hundreds of gallons of water to send that waste on a flume ride into a massive water reclamation facility.

Human waste is 90% water, and a composting system that's part of any composting toilet helps to remove the moisture while drastically reducing the amount of water used in the process.

Did you know that the average American uses around 100 gallons of water each day? That's not because of your new commitment to hydration, that's mostly from flushing the toilet. These efficient units reduce water usage, thereby lowering your utility bills and reducing your environmental impact.

Composting Toilet System
Composting Toilet System
On the Throne, Off the Grid

So who needs a composting toilet? The self-contained design with low water-requirements have obvious benefits for rural homes, cabins, RVs, tiny homes and even boats, but a composting toilet can offer extreme financial advantages when used as the primary toilet in most homes. As a money-saving measure or an effort to do your part for the environment, a composting toilet makes a difference. In more remote settings where connection to local utilities can be prohibitively difficult if not impossible, a composting toilet gives you all the necessary facilities without the unpleasant realities of a cistern or septic tank.

That's the Fresh Smell of Science

We weren't kidding about the no-stinky-smells claim, so if you're looking at a composting toilet to replace a waterless toilet, take a deep breath and smell the future. Waterless toilets that you'd find in cabins, RVs or in rural settings would often function no better than an old-timey outhouse, with waste just sitting in a container beneath the commode. A composting toilet incorporates a simple ventilation system while the waste is quickly broken down, thereby eliminating the smell. That's the sweet smell of progress.

Central or Self-Contained?

You can just dip a toe (figuratively) in the composting toilet world, or you can (again, figuratively) dive right in to composting toilets, but no matter the level of commitment, there's an option for you.

Self-contained composting toilets are the most common and are only slightly larger than a standard commode. Requiring only a few minutes of maintenance a month, these units handle all the basic functions and some even incorporate an electric heater to speed up the composting process.

Composting Toilet
Composting Toilet Technical Drawing

Waste is collected in an internal drum and manually dumped as compost into a finishing drawer as the drum fills. A bulking agent is generally added to aid in the process. Compost is manually enabled by rotating the drum, or operating a handle. Install it in your weekend cabin or replace that chemical monster in your RV.

Tiny Home
Trending Location: Tiny Homes

A central unit requires a bit more effort to install, but the potential benefits makes it worth the trouble. Equipped with an effective plumbing and venting system, a central unit connects one or more commodes to a single composter. In an office building, home or multi-family dwelling, this setup can help you realize significant utility savings while creating a more useful amount of soil-enriching compost.

The Science Behind It

Whatever compost toilet design you think is best for you, they all have the same basic needs for proper functioning: humidity and temperature control. The bacteria that break down waste need a temperature that's comfortably above 100°F for fast decomposition and the humidity level must be kept at a proper balance.

Composting toilets of the more advanced sort feature electronic control systems that monitor and maintain heat and humidity. The simpler, non-electric models will offer a slower decomposition process and have limited evaporative capacity. After a month or two, simply empty the tray. You'll see that the waste is reduced to about 10% of its original mass.

But What About Toilet Paper?

Whatever you want, as much as you want. We promise. Just keep your kids from throwing it in the neighbors' trees.


Before installation, check with your state, county, or municipality to find out if there are any regulations that cover composting toilets and permitted uses of "humanure" (some states don't permit fertilization of food-producing plants due to fears of potential pathogens). In some locations, you may also need to inquire about graywater regulations (i.e. disposal of non-toilet sewage water from sinks and showers).

A typical composting toilet is just a bit bigger than a standard flush toilet. It has a vent stack of PVC pipes that evacuates odors to the outside air; homeowners usually have the option of installing the vent up the inside wall or through the wall and up the outside wall. The toilet's overflow hose should be connected to protect against emergencies; make sure it drains to an approved container or disposal system.

After installation, you'll need to establish the compost. This can take a few weeks, and may require some adjusting. A mix of peat moss, pine shavings, and microbes starts the process. The moisture level is just as important as the oxygen level. Odor is a sign of too much moisture. Add extra peat moss to dry it out. If it's too dry, composting slows down or stops; add moss and warm water. After each use, drop in about 1/2 cup of pine shavings.