What is a Composting Toilet?

A composting toilet, by its most basic definition, is a type of commode that converts waste into compost, black dirt that can be tilled back into the soil. The most important and essential goal of a composting toilet is that the end product, the compost, should be completely odorless and harmless; it is essentially the same material that you'd go to a garden center or nursery to purchase by the bag or truckload. There are many different types of composting toilets, ranging from the very primitive to modern, high tech systems that look very much like a regular porcelain toilet fixture, some even flushing with water like a normal toilet, too. For the purposes of this article, we'll focus on the higher end units.

Around the world, there are several dozen manufacturers of modern composting toilets. Some of the most well known manufacturers include Phoenix, Sun-Mar Corporation, Biolet, and Envirolet. Of these, each company's products perform in slightly different ways, but all achieve the same end result. No matter where a composting toilet is installed, whether it's a residential, commercial, or outdoor application, the critical requirement is always the same: the unit must operate odorlessly. While each system achieves odorless operation in a slightly different way, they all rely on some kind of ventilation system, and often times a fan that is powered by an electrical plug (into an outlet) or, where electricity is not present, a 12 volt battery and/or solar panel.

One of the most important keys to an odorless composting system, no matter whether you are composting food scraps, yard clippings, or human waste, is that the compost must remain aerobic. Aerobic composting requires oxygen to feed the bacteria that break down the waste. The primary benefits of aerobic composting are that it's fast, with raw material converting into finished compost in a matter of months, and it's odorless. Aerobic bacteria do not create any noxious gasses as a byproduct of the decomposition process.

To this end, every modern and high tech composting toilet should have some method of aeration of the contents. This is usually achieved by rotating a drum that the contents are held in or rotating some kind of tines that stir the compost in its holding chamber. In virtually every case, it is not required that you come into contact with the compost or any raw material in order to do the aeration. Modern composting toilets feature the ability to aerate the material without ever opening the drum or holding chamber itself.

The fact that modern composting toilets rely on aerobic composting is what sets them apart from their primitive cousin. Old composting commodes, often times nothing more than a bucket with a toilet seat attached to the top, have no means of aerating the material. Any organic matter that sits and is not aerated, regardless of whether its vegetable peelings or human waste, will begin to smell. This is because the pile will quickly convert to anaerobic compost, meaning that the decomposition process slows significantly and the anaerobic bacteria begin to give off methane and sulfate gasses as a byproduct of the composting process. The goal of every modern, high tech composting toilet is to avoid this possibility all together.

Composting toilets are enormously beneficial to the environment because they reduce our consumption of fresh water for transporting waste. They also reduce potential contamination of groundwater in developing countries where there is no infrastructure in place for waste disposal. Even in areas where septic systems are being used, composting toilets are a much less expensive, longer lasting, and more ecologically stable alternative, because they reduce nutrient load on the aquifer. For anyone building a new home, office, or simply replace an old, leaky toilet, modern composting toilet systems are something worth considering.