Continuous composting toilets

Composting toilets are becoming an increasingly popular alternative to conventional toilets, especially outside of urban centres where fresh and/or waste water services are not available. Composting toilets can significantly reduce a building’s demand for fresh water as they eliminate the need for flushing. They generate virtually no wastewater, which in turn reduces the need for wastewater treatment and minimises the impacts of development on groundwater sources. Additionally, composting toilets allow human waste to be turned into nutrient-rich compost that, under the right conditions, can be used as garden fertiliser.

The key to successfully operating a composting toilet is maintenance. The Phoenix Composting Toilet has been designed to make this process as simple as possible, ensuring an optimal end result and a pleasant experience for users.

What makes the Phoenix Composting Toilet different?

Components of Phoenix Composting Toilets (image courtesy of Camp Glenorchy)

In its simplest form, the Phoenix is made up of a waterless toilet located directly above an insulated polyethylene tank, equipped with a set of built-in rotating tines, an electric fan and a vent pipe. In the tank, waste gradually builds up and decomposes through the action of aerobic bacteria, moisture and heat. Using a crank handle, the tines are rotated periodically to mix this waste and ensure it’s getting enough oxygen. As it decomposes, older waste makes its way to the bottom of the pile until it finally falls as compost - reduced 80 to 90% in volume - on a tray where it can be easily removed, typically once a year.

When people open the toilet lid, the electric fan pulls air from the room into the tank, which is then expelled through the vent pipe that usually extends up to the roof. This means each time the Phoenix is used, the bathroom will actually smell better than before. Instead of flushing water, people can add white wood shavings after they’ve used the toilet to make the waste more porous. However, in public facilities these shavings can be added directly to the tank as part of routine maintenance. Liquids are separated from solids through a drain at the bottom of the tank and are automatically resprayed on top of the pile to maintain moisture. Any excess liquids are drained to a leach field or a holding tank.

When is the right time to think about them?

The Phoenix Composting Toilets come in multiple sizes that suit a range of projects and climates, from off-grid huts in remote locations to multi-story commercial buildings such as the Bullitt Center in Seattle. However, for these composting toilets to work in the best way possible, there are a few space requirements that need to be considered early in the design process:

  • The tank of the Phoenix must be located directly below the toilet. For one-story buildings this means that a basement might be needed. This is the case at Camp Glenorchy Eco Retreat which has 21 toilets installed on site: six in the Amenities Building, one in the Maintenance Building and two in each of the guest cabins. Projects on sloping sites can take advantage of the terrain to place the tank below the toilet. This will reduce excavations and allow easier access to the tanks for maintenance.
  • The tank must rest upon a smooth, level, flat surface, preferably inside a heated or well insulated space. Even though the Phoenix Composting Toilet is frost-safe, the composting process will be much slower when the tank is cold. An area that remains at a stable temperature year-round will help the process to continue at a steady pace.
  • Convenient access, good lighting and ventilation, as well as adequate space in front of the Phoenix, must be provided for maintenance.

Phoenix Composting Toilets are designed and built by Advanced Composting Systems in Montana, US. Tanks are available in a range of residential and commercial sizes, and alternatives for buildings with toilets that can’t be placed directly over tanks are provided by the company.

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Advanced Composting Systems

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