How dry toilets work

How dry toilets work

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If I say "dry toilets" ... especially forget the old hole at the bottom of the garden! Think instead of "saving water", "respecting the environment", "enriching the earth" and "treating waste". Our northern European neighbors are already won over, but yet only 1,500 French households are equipped; dry toilets are in fact poorly known in France. To take stock of this ecological system, Christophe Elain, author of the book "A little corner to relieve the planet", answers our questions to better understand the operation, advantages and disadvantages of dry toilets. Interview by Lise Lebrun

How do dry toilets work?

The main characteristic of dry toilets is that they operate without water. The excrement falls into a receptacle in which it is stored for a longer or shorter duration, depending on the model chosen. There are different techniques but the most ecological is the one that ensures the composting of excrement. For this, each time you go to the toilet, a material rich in carbon is added - sawdust and / or shavings for example. This addition makes it possible to obtain a good carbon / nitrogen ratio and ensures optimal composting because the excrement is rich in nitrogen. However, there are models of toilets that operate without adding carbonaceous material.

How to install dry toilets at home?

Installing dry toilets is very easy, especially if you choose a "wooden box" model, in which a simple bucket is placed. It then suffices to place everything on the ground at the chosen location. Other models require the outlet outside of a pipe for ventilation. Some large capacity toilets require the installation of a downspout when the receptacle is placed in the room below (basement, garage). If not, it is also possible to create your own model , fitted to the room, with the materials of your choice, giving free rein to your imagination - to build yourself or by calling on a carpenter or mason.

How much does such a system cost? and what are the savings compared to "conventional" toilets?

The cost of a dry toilet varies widely depending on the model chosen. This goes from a few tens of euros for a small wooden box, self-built, to 800 or 1000 euros for a manufactured model, or even a little more if it is a more sophisticated model requiring some work of installation. Use a dry toilet rather than a flush toilet saves up to 15,000 liters of water per person each year, or nearly € 200 less in expenses for a family of 4.

Does it smell bad?

When a carbonaceous material is added, such as sawdust for example, this has, among other functions, to allow the unfolding of a physicochemical process which prevents the development of odors. For models without the addition of carbonaceous matter, a ventilation system or a separation of urine and faeces prevents odors from developing. With proper toilet management, these dreaded odors are not to be feared and are at most a small rare and temporary annoyance as it also happens with a flush toilet.

Is it possible in town?

It is possible to install dry toilets in the city because most of the models are intended for the interior of houses or apartments. In a building, if the chosen model requires the installation of a ventilation or evacuation pipe, it is of course essential to first check what is possible with the co-owners. In addition, it is necessary to have a place to empty the contents of the toilets and to compost it. It is therefore necessary to have a garden or to find somewhere a person accepting that one uses for this function a small site on his ground. This lack of space to compost is often the limiting factor in the city . Otherwise, there is always the possibility of putting the contents of the toilet in the trash but this solution, not at all satisfactory, is to be avoided.

How is installing a dry toilet environmentally friendly?

If the arrival of flush toilets and everything in the sewer offered a solution for the evacuation of excrement, very quickly this system showed its limits. In fact, introducing excrement into the water cycle generates major problems. The water which arrives in the toilets is first treated to become drinkable then we pollute it with our excrement, the whole being then evacuated towards a purification station. After a treatment, generally ineffective, the water is discharged into the rivers and plays a very important role in polluting them. In addition, water always precious obviously for food or household uses is very rare in some places so using it for toilets is an aberration and an incredible waste. Dry toilets prevent this and, thanks to composting, the elements that come from the soil come back to it and feed it in the form of humus. By adopting dry toilets we act responsibly respecting and maintaining the cycle of life .

Where to find the sawdust? How much does it cost ?

In sawmills, sawdust is available in large quantities, free of charge or at low cost. But for those who do not have a sawmill in their region, it is often possible to collect it from carpenters, avoiding sawdust from treated wood as much as possible. Otherwise, in garden centers, there are sold bags of litter for horses and pets made up largely of dusted shavings, which are well suited for dry toilets. A 550 liter bag (compressed and therefore compact) costs around 14 euros.

What are the disadvantages of dry toilets?

If the chosen model has a 15 or 20 liter bucket as a receptacle, it will be necessary to empty it every 4 to 6 days. With other models, oil changes will only be necessary once a month or even only every 6 months or once a year. Whatever the frequency of emptying, it is this constraint, as well as the monitoring and spreading of compost, which many consider to be the main disadvantages of dry toilets. You have to be ready to assume this when choosing these toilets, even more so when the land provided for composting is not next to the house or building. Compared to the water which takes care of this evacuation without our intervention, this is indeed a constraint but quickly relativized when we perceive how important it is to assume entirely what we produce if we really want to ensure the survival of our dear planet.

For the moment, dry toilets are not the norm, so they require make the choice to oppose the dominant model and be ready to face again on the part of some laughter and sarcasm . It is currently, for the vast majority, socially easier to install a flush toilet than dry toilets. However, this drawback is not inherent in dry toilets and should disappear quickly given the constantly growing number of those who see the relevance of adopting these toilets without water. For more information : A little corner to relieve the planet of Christophe Elain (288 color pages) at Editions Eauphilane, 2007 (Tel. 05 53 91 22 29; [email protected]; 10 € + 3 € postage; //


  1. Baldassare

    yes ... such a thing would not hurt me)))

  2. Cain

    It is remarkable, a useful idea

  3. Maughold

    Rather valuable answer

  4. Vim

    A good post, after reading a couple of books on the topic, still did not look from the outside, but the post somehow hurt.

  5. Tolrajas

    Is this a prank?

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