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How Do Composting Toilets Work?

written by: Rose Kivi•edited by: Niki Fears•updated: 2/28/2010

Environmentally friendly composting toilets conserve precious drinking water. Composting toilets do not use water, but instead recycle human waste into nutrient rich compost that can be used to fertilize soil.

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    How Does a Composting Toilet Work?

    The two main types of composting toilets are homemade and commercial made. Most people consider the advanced design of commercial composting toilets a more desirable option than homemade composting toilets. Homemade composting toilets generally require a lot of maintenance and involvement in the process of the composting. Commercially made composting toilets, compost the waste quicker and with little required involvement.

    The homemade composting toilet is usually very simply made. Generally a toilet seat cover is fitted on top of a five gallon plastic bucket and is placed inside a custom wood box for aesthetic purposes. The bottom of the bucket is covered with a layer of substrate of either dried crushed leaves, peat moss, wood shavings or a layer of sawdust. After a person uses the toilet, they cover their waste and toilet paper with a layer of substrate to prevent odors. When the bucket is filled, it is emptied into an outdoor composting bin to sit and turn into compost.

    There are many different models of commercially made composting toilets. Most of them have slight variations in design, but they all work using the same principles. The commercial models are made out of plastic or fiberglass and look similar to conventional toilets. A substrate such as peat moss is added to the commercial composting toilet at installation and once a day for common household use, to assist in the breakdown of waste into compost. The toilets contain a holding tank which is closed off from view, that holds the waste and substrate. Waste that is flushed enters the tank where it will be turned into compost.

    Commercial composting toilets are equipped with fans, heaters and vents to assist and speed up the composting process. The fans, heaters and vents, remove much of the water content of the waste, making the amount of waste smaller. Smaller amounts of waste mean that the toilet does not have to be emptied as often. A commercial composting toilet that is used regularly in a household will need to be emptied approximately every two to three months. The toilets are typically emptied through a drawer that slides open at the bottom of the toilet. Because the fans, heaters and vents convert the waste to compost at a fast rate, what is emptied from the toilet is already converted into compost.

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    Do Composting Toilets Smell?

    Composting toilets do not smell. The use of substrate in homemade composting toilets prevents odors. Fans and vents, combined with substrate prevent odors in commercial composting toilets. The finished product of compost does not have a bad odor.

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    Are Composting Toilets Safe?

    The composting process destroys harmful bacteria, viruses and parasites. The toilets do not use water and therefore do not contaminate the water supply through sewage line breaks or leaks. Because the waste is from humans, experts suggest not using the compost on edible plants or by underground water sources unless it has been composted for at least a year. Some experts suggest two years. To be safe, it is wise not to use the compost on edible plants.

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    Laws and Regulations

    Check your local building regulations to determine if the use of composting toilets is allowed in your area. The use of environmentally friendly composting toilets has not caught on in all areas and is not legal in many states.