How Do Composting Toilets Work?

can be a clean, environmentally friendly alternative to traditional water-based toilets. They utilize natural processes of decomposition and evaporation to produce an end product which may be used safely as a nutrient rich fertilizer, and which contains no harmful pathogens or viruses¹.

Essentially, there are three functions which a composting toilet must perform in order to work successfully on a household scale. They must:

• Breakdown human waste and toilet paper rapidly and without odours.

• Create a finished product which is clean, contains no harmful diseases or pathogens, and is easy to handle.

• Evaporate excess liquids quickly and efficiently.

While there a number of different companies who produce composting, waterless, or ‘eco’ toilets, they all utilise the same basic principles. The toilets themselves can vary from simple bush long drops through to complex systems designed for flawless household use. Although they have been used in Eastern societies for hundreds, if not thousands of years, composting toilets have only recently begun to become popular in Western society².
 

How does it work?

The main principle behind the workings of a composting toilet is the aerobic breakdown of faeces and urine into a safe product. They are designed to provide relatively dry, oxygen rich conditions which allow bacteria and other micro-organisms to survive and prosper. It is important to note that the composting waste must be kept dry so that anaerobic decomposition doesn’t occur – this will cause unpleasant smells to radiate throughout your house.

In most commercially available compost toilets, this is done by separating the liquid and solid parts of our waste as they enter the toilet. The solid part enters a holding chamber tank, where the composting occurs. The liquid portion enters an evaporation tank, which is designed to remove it as fast as possible. The final residue which results from the evaporation process must be added to the solid composting mix, in order to render it harmless and free of pathogens or viruses².

If done correctly, the final product of the composting process is tiny compared to what enters the toilet. Up to 90% of faecal matter is water, and once this has been evaporated off, very little is left. Odours are generally eliminated by means of air flowing over the composting material and to an outside vent. This can be accomplished by a fan or some other mechanism, and also aids the evaporation process³.
 

Environmental benefits of composting toilets

Not only are composting toilets an easy, efficient, and trouble free way of disposing of your waste, but they also have a number of environmental benefits. Number one: they don’t use water, which can make a significant difference to your household water consumption, and can reduce the amount of polluted waste water which escapes into the ocean. The average household flushes the toilet around 5000 times per year. The amount of water used with each flush can range from around 6 litres up to around 25 litres in older toilets – if the average flush is 10 litres, then every toilet uses 50000 litres of water per year. If composting toilets were to become widespread, the water savings would be immense³! Composting toilets produce no pollutants, and capture the nutrients contained in human waste in a way which can then be integrated back into society as a fertilizer in a safe, chemical free manner.

References

¹ http://www.letsgogreen.com/how-composting-toilets-work.html
² http://www.eco-toilets.co.uk/eco-toilet-info/
³ http://www.sun-mar.com/tech_how.html