With no need for water, dry toilets make safe waste management possible where standard wastewater treatment systems are impractical. They’re ideal for homes in remote areas or regions where water shortages are common. Dry toilet systems vary in their requirements and the type of waste they produce. The system that will best meet your needs depends on your available space, source of power, whether or not you want compost, and your budget.
Composting Toilets
The most common type of dry toilet, a composting toilet, collects waste in a sealed chamber beneath the toilet seat. The system takes advantage of the natural decomposition process to turn this waste into nutrient-rich organic material known as compost. Because of this, composting toilets can process only human waste and toilet paper. Anything else can harm the microorganisms that break down the waste.
Human waste is mostly water. A composting toilet evaporates this water by using an electric ventilation fan to draw air through the collection chamber. The resulting carbon dioxide and water vapor are carried away through the vent system into the outdoor air.
The remaining solid waste material gradually moves down a sloping floor as it decomposes and more waste is added. It eventually passes into a hummus chamber where you can access the ready compost. Liquids drain away into an absorption trench. In most home systems, the composting chamber is installed below floor level, so the toilet can’t be easily moved. Small self-contained systems for tiny houses and mobile use are an alternative.
These toilets require some monitoring to keep the compost well aerated. In freezing temperatures, the decomposition process might stop, but it will start again when the weather warms up. When working correctly, they produce very little odor.
Every one to six months, depending on how often the toilet is used, you can remove the compost to use on your lawn, landscaping plants, and fruit trees, although it’s not suitable for edible plants.
Incinerating Toilets
Incinerating toilets collect waste in a holding tank below the seat and uses high heat to burn the waste to ash. Combustion gases are released through a vent to the outdoors. The resulting ash is sterile, so you can throw it away with your normal household trash. This convenience makes the toilets practical for locations where composting isn’t an option. To use the toilet, you’ll need to line the bowl with a manufacture-provided paper liner first, then press a button or pedal to release the liner and the waste into the holding tank.
Both electric and fuel-burning models are available, making these toilets ideal for remote areas. Electric models, which can run on mains power or batteries, can handle several uses before you’ll need to run the incineration process. The process lasts 30 minutes to around an hour. Depending on the design, fuel-burning models can store up to 60 uses before incineration is necessary. Because there’s more material to burn, the incineration process takes somewhat longer than for an electric model.
Typically, these toilets produce even less odor than composting toilets, although you’ll probably notice a slight burning odor when the incineration process starts. Spraying an aerosol masking foam into the holding tank helps keep odors down between incinerations.
The ash container should be emptied daily to weekly depending on use and capacity, but the process is faster and less labor-intensive than removing compost. Unlike composting toilets, they aren’t sensitive to temperature. Most models aren’t anchored to the floor, so they’re easy to move. You’ll only need to relocate the vent pipe. On the downside, they’re several times more expensive than composting models, but don’t provide compost that can benefit your landscape.
Urine-Diverting Dry Toilets (UDDT)
A UDDT collects urine from the front of the toilet, while solid waste falls through a hole in the back and collects in a separate chamber. A small amount of material such as soil, sawdust, sand, ash, or lime is then poured into the hole to speed the drying process, reduce odors, and help kill off pathogens. A ventilation pipe leading from the solid waste chamber carries away moisture and odors. When the solid waste chamber is full, the dried material can be removed and composted.
This differs from a traditional composting toilet, in which liquid and solid waste end up in the same chamber. With the two products separated and contained in sealed chambers, the toilet produces next to no odor. UDDTs are easy and cheap to build, making them popular in less developed areas.
The main drawback is that you’ll need to take care when using the toilet so that no waste material enters the wrong chamber. If this happens, the toilet can become clogged and fail, causing odors.
Freezing Toilets
These dry toilets aren’t common, but they can be useful in locations with mains power, but no sewage system. Waste is collected in a bag-lined holding chamber contained within the toilet system. Using the same process as an ordinary freezer, the toilet quickly freezes the waste to slow microbial activity and prevent odors.
Most operate at a temperature between 0 to 7 degrees, a little warmer than the average freezer. When the toilet is full, you can empty it into a composter for kitchen or garden waste to get compost for use on non-edible plants.
Freezing toilets don’t need ventilation systems, so they’re entirely self-contained. That makes them easy to install and highly portable. Heated seats and other features protect you from the cold of the holding chamber. The purchase price is typically a little less than for an incinerating toilet, but still higher than a traditional composting toilet. These toilets freeze slowly at room temperatures above 75 degrees, so they’re not ideal for unairconditioned homes in hot climates.
Whether the traditional options aren’t practical for your home or you just want to reduce your water consumption, a dry toilet offers a safe, convenient alternative for managing your sanitation needs.