Smell of composting toilet: Does something stink here?

The biggest concern of all those who deal with the topic of motorhome toilets/ camping toilets and ultimately with the composting toilet is the possible unpleasant smell or even stench.

On the one hand, many motorhome drivers and van owners are concerned with an alternative toilet because they notice an unpleasant smell from their cassette toilet and this usually spreads throughout the entire vehicle.

They want to improve the situation and understandably have concerns about the odour.

On the other hand, of course, everyone knows that excreta smells unpleasant, especially intensely after having recently gone to the toilet. Now many also imagine several poops collected in a bucket, perhaps stinking away!

In this article we want to show why the composting toilet or dry composting toilet does not stink.

Is the smell of a composting toilet unpleasant?

Let's at least answer that question right at the beginning, before we get into the details.

NO, a composting toilet does not smell and it certainly does not stink.

The composting toilet has been used and appreciated for over 90 years. Certainly not without reason.

composting toilets have also gradually been available for motorhomes for about 20 years. However, demand has grown particularly strongly in recent years.

Why? The dry composting toilet makes you independent of disposal stations. The emptying intervals are significantly longer for solid waste and you do not need any additional water for the composting toilet.

As long-term vehicle travel becomes more popular, as does free, independent standing, the demand for suitable toilet systems is also growing.

Another frequently cited reason for changing the cassette toilet is the unpleasant odour. 

What causes the unpleasant odour in chemical toilets and bucket toilets?

The stench is caused by the mixing of excreta. Nature has already provided for the separation composting of urine and faeces in almost all living creatures. Excrement has a different exit than urine. However, some animals have a common excretory outlet, the cloaca. The ureter and intestine open into the cloaca and are excreted together, as in birds. However, there is no joint collection of both excretions in the body over a longer period of time in any living creature.
When the excrements are mixed, the odour is caused by the release of various gases such as hydrogen sulphide, ammonia and methane. Various bacteria and yeasts cause the odours that we can then perceive through their work of decomposing the nutrients. Bacteria, yeasts and ultimately the resulting enzymes are even more active in the liquefied mass, as is common in a cassette toilet. The air supply to the mixture also supports the odour.

Cassette toilets prevent the activity of bacteria by using liquid additives in the form of chemicals or biological products, so that odour formation is minimised. However, some chemical additives should be used with caution, as mentioned in this post: "Why it pays to switch from a cassette toilet to a separation toilet", as they cause harm to humans and animals. The biological products work via effective microorganisms or enzymes, but they have their price.
Alternatively, some users of cassette toilets use SOG systems. In this case, the odours are eliminated by creating a vacuum in the toilet.

Famous composting toilets

How does this strong urine smell sometimes occur with classic toilets?

Fresh urine does not actually smell if you drink enough of it. However, certain foods, such as asparagus or medication, can cause urine odour.

We have already dealt with this topic in our article on cleaning a urine-diverting toilet. It should be mentioned again here that urine only begins to decompose after a long period of storage and thus the odour formation.

The well-known urine smell is primarily caused by the combination with water, especially with the lime dissolved in it. Another factor responsible for the odour is the urine scale that builds up over time.

So the longer urine is collected, the more likely it is that odour will be perceived. For this reason, most urine-diverting toilets have a maximum of one 10-litre canister, which lasts for about 2-4 days.

Why is there no unpleasant odour with the composting toilet?

Bausatz seitlich flach

The naturally created separation of urine and faeces is continued in the composting toilet by using a urine separator. The urine runs into a canister and the faeces fall into the container at the back.

Because the urine is stored for 2-4 days, there is no odour. From time to time, however, we recommend cleaning the urine canister from urine scale. Read more about this in our article: Cleaning a urine-diverting toilet.

Fresh excrement naturally smells due to the chemical compounds it contains, such as hydrogen sulphide, which is produced by putrefactive bacteria.

Other odours come from the putrefactive processes of amino acids. These odours dissipate over time, just like in the toilet at home. The drying of solids is the open secret behind a functioning composting toilet.

You can achieve this by using a scattering material and/or a fan. The aim of both options is to remove moisture. As long as the faeces are moist, they smell.

By removing the moisture, the processes described above change. Certain enzymes and gases only form in the moist or liquid excreta mixture. The solids decompose more slowly and through other biological processes.

For these reasons, there is no unpleasant smell in a composting toilet.

Fan or litter or both?

There are now many users of composting toilets and each has its own technique. Some use only litter.

This is fine, because all the moisture is absorbed by the litter and released through the fibres so that everything can dry off. However, if the litter is collected for a longer period of time, condensation will form over time.

This can be prevented or regulated by leaving the lid of the composting toilet open from time to time or by using a fan. This allows the moisture to evaporate.

The smell would possibly occur if the condensation moisture collects in the composting toilet and drips back onto the mass. This causes the moisture content to rise again and odour to develop.

A fan can be used as a support or alternative to the litter. This ventilates the moist warm air outside and allows the faeces to dry.

The fan also removes freshly formed odours, so that the overall odour formation is somewhat reduced.

Some composting toilets are designed in such a way that the solids can only be dried with a fan. Here, litter is dispensed with completely. The fans used have a very low power consumption. You don't have to worry about this, even with continuous use.

By using a fan, however, you can collect for longer. Without a fan, the disposal intervals are somewhat shorter.

Odour when emptying the composting toilet

The collected, dried solids no longer smell like faeces or excrement, as one would expect. Therefore, disposal does not pose any challenges. In the case of composting toilets with a solids container without an agitator, such as the Trelino L - Beautifully Designed composting Toilet, disposal is altogether uncomplicated.

A compostable bag is placed in the solid waste container, which is simply tied shut and thrown into the nearest waste bin. In the case of composting toilets with agitators, such as the NaturesHead composting toilet, the solids container is transferred into a compostable bag and then disposed of.

Here we would simply like to refer to a few testimonials from composting toilet bloggers and users. Two of them have a composting toilet with agitator.

Jürgen from writes: "No, it doesn't smell. At least not like manure, urine or excrement. It sometimes smells earthy, like forest floor, but only when the fan isn't running."

Nima from writes: "We've been using our divider toilet without a fan for almost eight months and get along very well."

Harriet from writes: "The smell of the solid waste tank is not faecal, more like earth. And yes, I've put my nose right in it."

About 98 % of users of composting toilets make only positive statements. Many users now write about their experiences. The composting toilet has proven itself through and through. There is no mention of any unpleasant odour with any composting toilet.


A composting toilet is a wonderful solution, especially if the issue of odour has ever been a concern with your toilet.

composting toilets don't stink, they don't smell unpleasant either! Make sure that the moisture can be transported away and you will be very happy with your composting toilet.

In this article, we have explained the background of odour formation in detail. Now you understand the principle behind it and can continue to work with the composting toilet without worrying.

We are also happy to help you with any questions you may have. Here you can delve deeper into the topic and find out how you can dispose of the faeces from your composting toilet:

What do I do with the faeces from a dry composting toilet? Suggestion for composting