Composting Toilet Inspection

by Nick Gromicko, CMI®
A composting toilet is a system for collecting human waste which is then processed by aerobic microbial activity that decomposes it and kills off potentially hazardous Outdoor composting toiletpathogens. Composting toilets are environmentally friendly; they do not require water or sewage treatment, and they produce an end-product called humus, which is suitable for fertilizing trees and landscapes. They are more deliberately implemented than pit toilets or pit latrines, which are essentially just waste ditches that can pollute groundwater.  

Facts and Figures

  • Composting toilets have been commercially sold for more than 30 years, starting in Sweden, according to the EPA.
  • Humus decomposes to only 10% to 30% of its original mass.
  • Composting toilets may be implemented in some urban areas, including tall buildings. One such example serves at least 300 people at the University of British Columbia in Canada.
  • Composting toilets are becoming increasingly popular in public areas, especially in Sweden and elsewhere in Europe.  Implementing compost toilets can reduce overall water usage up to 50%, according to Composting Toilet World.

How does a composting toilet work?

Composting toilets can be built indoors or outdoors, ranging from simple, do-it-yourself kits to expensive and elaborate manufactured systems. They employ sufficiently dry and oxygenated conditions, in contrast to a septic system. Users generally apply small amounts of absorbent materials, such as peat, sawdust, or other carbon-laden products after each use to soak up superfluous fluids, and to aid in aeration for enhanced aerobic action. Vents run upward and outward, circulating air and eliminating odors. Some designs necessitate infrequent aeration by hand, for example, by rotating an in-build drum. Fans may be installed to increase air flow in units with electricity. Temperature is also an important factor, as increased heat tends to accelerate the decomposition process. Heaters are oftentimes utilized to maintain sufficiently high temperatures, especially in cold climates and where electricity is available.
A few variations on the basic system include the following:
  • Remote composting is a system in which collected materials are manually transported to a composting bin that has already been established to process yard and kitchen waste. 
  • Continuous composting is a simple system in which waste material decomposes in the same receptacle that it is deposited in. Since the material is not moved from one location to another, microbial activity is unimpeded, and the pile's work goes faster as heat builds up.
  • Batch-composting employs at least two composting receptacles that are alternated so as to allow for one to process material as the other collects new waste.
  • Dry composting toilets are those that separate urine from feces as a means to diminish moisture and the nitrogen content of the compost material. 

Advantages of Composting Toilets

  • No water is required for composting toilets because they employ aerobic activity to break down waste. They are thus a viable option in locales lacking access to running water.
  • Less water usage means decreased stress on freshwater supplies, and a lower household water bill.
  • No plumbing, septic tank, or sewage treatment is required of composting toilets, so they are relatively simple to install.
  • Local soils maintain fertility, as nutrient-dense humus is added back into the ground.
  • Compost toilets are adaptable to both rural and urban environments, depending on local ordinances.
  • Composting toilets are a viable option where septic systems are not practical because of rough terrain or adjacent wetlands, for example.
  • Implementing composting toilets is a reliable means of remediating pathogens and prohibiting their release into the environment.
  • End-product humus is safe and easy to handle, if the system has been installed properly.
  • Kitchen waste may be added to composting toilets, in many cases.
  • No special skills or knowledge is required for the construction and maintenance of composting toilet systems.
  • Batch-composting systems are expandable for added capacity. 

Disadvantages of Composting Toilets

  • Composting toilets require proper commitment, attention and maintenance. Receptacles may need to be emptied between every few months to every few years.
  • Waste material may need to be tamped down periodically in order to allow for uniform coverage and aeration.
  • Emptying the humus may be unpleasant if the system is not functioning properly.
  • Some systems allow for excrement to remain visible.
  • Smaller units may not have a sufficient capacity for high usage.
  • The systems may be aesthetically unappealing.
  • Some systems require access to electricity.
  • Factory-built systems may be expensive.
  • The units require periodic cleaning. 

Compost Toilet Hazards

  • Using improperly decomposed humus may have negative consequences for soil and for human health.
  • Lack of cleaning may result in odor and a negative impact on health.
  • Extra caution must be taken with excrement that originates from a diseased population. 


  • Local and state guidelines should be followed as they pertain to sanctioned handling and use of end-product humus. Users should also find out what designs of composting toilets are allowed in their municipality.
  • Moisture, aeration and temperature levels should be monitored and adjusted, as appropriate.
  • Humus should not be used on crops that are intended for raw consumption.
  • Humus should contain no more than 200 parts per gram of fecal coliform.
  • A fan that is operating properly should drive air out of the vent.
  • The vent pipe should be of sufficient height so that expelled air does not cause odor problems around the unit.
  • The evaporation tray should not be blocked in units that separate urine from fecal matter.
  • The vent should have a screen attached to it to prevent flies and other insects from entering the unit.
  • The proper ratio of carbon to nitrogen should be about 30:1.
  • Harsh soaps and detergents should be avoided because they could slow the decomposition process. 
  • The unit should be sufficiently clean so as to minimize human contact with waste matter.

In summary, composting toilets offer significant advantages when implemented properly, and when local ordinances and guidelines are followed.