Do Composting Toilets Smell? (Solved & Explained!)

A well-maintained modern composting toilet should not smell, especially if it has separate chambers for solid and liquid waste. You can keep your composting toilet odor free by emptying the compost as required, installing your vent and fan correctly, and supporting the composting process through optimum levels of moisture, temperature and air circulation. 

Our quick and simple guide below tells you all you need to know to keep your composting toilet smelling sweet in a range of common settings. 

Do composting toilets smell?

When composting toilets are properly installed and well-maintained, they should not smell more than other toilet types and may have significantly less ongoing odor than some (e.g. chemical toilets). 

There are many different types of composting toilets available ranging from very basic (a bucket and a bag of sawdust) to more complex (a three-chambered toilet which automatically separates liquid and solid waste and optimizes the composting process). 

Composting toilets do not use water to flush away human waste (urine, excrement and toilet paper) into sewers. Instead, they rely on aerobic bacteria to break down waste into harmless, odorless and even useful, byproducts.  

Smells are most likely to arise when a vent or fan are not working properly, or when levels of moisture, heat or oxygen in the compost fall outside the range required for efficient aerobic breakdown of waste.  

For example, too much liquid in the compost can encourage development of anaerobic bacteria which break down waste by odor-producing mechanisms, leading to a sewage smell. Composting toilets with separate chambers for liquid and solid waste avoid this issue. In single chamber toilets, the problem can be controlled by adding dry organic matter such as wood-chips to the compost to absorb excess moisture.   

Do composting toilets smell in tiny homes?

In any setting, a properly installed and maintained composting toilet should not smell. In tiny homes, it will be particularly important to fit vents and fans so that negative pressure carries away any smell before it can spread in the small space. 

Do composting toilets smell in RVs?

There are a range of composting toilets designed and sized specifically for RVs, although fitting vents may involve cutting a hole in the wall of your RV bathroom. 

Your toilet should be emptied regularly depending on level of use, to ensure that it does not become overloaded with solid waste which has not had time to compost. 

 

Do composting toilets smell in vans?

As with composting toilets in tiny homes or RVs, you should be able to install a composting toilet in a van without producing bad smells. Measure your van space carefully and read reviews thoroughly to ensure you buy the right composting toilet for your space and needs.  

Do composting toilets smell in boats?

There are particular considerations around managing composting toilets on boats. Not all models of composting toilet will be suitable for use on all types of boat. For example: 

  • Vents and fans might need to be modified to ensure they can be used safely end effectively on water. 
  • If at sea for long periods of time, there may not be regular opportunity to empty the compost bin and smells may occur for this reason. It is illegal to discharge human waste into the sea so composting toilet owners must wait until they are docked and then pump or carry their waste onto land. 
  • The pitching and rolling motion of a boat on water could cause waste to shift, mix or leak inside some composting toilets, leading to smells. 

If installing a composting toilet on a boat, you should research suitable models and seek reviews from owners who have used them on similar boats.

 

How do I stop my composting toilet from smelling?

The best way to prevent your composting toilet from smelling is to support an efficient breakdown of waste by aerobic bacteria, and discourage the growth of anaerobic bacteria which will produce bad smells. 

Efficient aerobic breakdown happens where waste is kept at optimum levels of moisture, temperature and oxygen. Depending on the type of toilet, you may need to add organic material, rake compost, empty bins, or rotate a drum to maintain the right environment.  

Peat moss, saw dust and fine wood shavings can all be used to control moisture levels in your composting toilet. Some composting toilet owners also add coffee grounds or composting worms to their toilets to reduce the chance of bad smells.

How bad does a compost toilet smell?

When composting toilets are properly installed and well-maintained, they should not smell more than other toilet types and may have significantly less odor than some (e.g. chemical toilets).

 

Do indoor composting toilets smell?

Indoor composting toilets do not have to smell any more than outside composting toilets. Modern indoor composting toilets often include vents and fans to carry away toilet odors and disperse them in the air outside.  

Can you pee in a composting toilet?

Yes, you can pee in all composting toilets although there are different considerations for managing moisture levels in composting toilets with a single chamber compared to two or more. 

Efficient and low-odor composting by aerobic bacteria requires that toilet waste is damp but not saturated. In a single chamber composting toilet, too much urine in the system could slow down the composting process, potentially allowing anerobic bacteria to thrive and create unpleasant smells. 

This risk can be countered by adding organic material (wood-shavings, coconut coir, peat mass etc..) to absorb excess liquid, trap odors, and support the aerobic breakdown of waste.    

Can you use baking soda in a composting toilet to reduce the smell?

Some composting toilet users may sprinkle baking soda into their buckets or systems to reduce odors when the toilet will not be used or cleaned for a period of time. 

Are composting toilets gross?

Composting toilets are far more cool than gross… 

They use the natural composting process to break down human waste into something useful, while saving the water which is used in flush toilets, and avoiding chemicals which could contaminate the environment. A composting toilet could save over 6600 gallons (24,984 L) of water per person each year! 

It is no wonder that governments choose to install them in national parks and remote facilities. Many research papers published in reputable US and European journals find composting toilets to be a viable and sustainable alternative to flush based sanitation.

 

How do you clean a composting toilet?

Different cleaning regimes should be used for different types of composting toilets. Always read the manufacturer’s instructions carefully and use only cleaning products compatible with your toilet. 

Some companies sell special cleaning products for use on composting toilets. Hot water with baking soda or vinegar can also be used to clean a composting toilet. Regular chemical cleaners or bleaches would interfere with the composting process and should not be used. 

A toilet brush can help remove stains from composting toilets with a bowl structure. Be careful when rinsing toilet surfaces in order to avoid saturating the compost and creating smells.  

Bucket composting toilets, or compost containers from more sophisticated units, should be emptied regularly into an outside compost bin or other safe dumping area, and then cleaned with hot water and baking soda, vinegar or a suitable cleaning product. 

Which composting toilet smells best?

Composting toilets with at least two chambers to separate liquid and solid waste are most likely to be odor free. When liquid and solid waste are mixed, anaerobic bacteria are more likely to thrive, breaking down the solid waste into ammonia and other by-products with a characteristic sewage-smell.  

How often do you have to empty a composting toilet to keep the smell down?

The frequency with which you need to empty your composting toilet will vary with the size of the toilet, the number of people using it, and the amount of toilet paper used.

Smaller composting toilets may need to be emptied every 3-4 weeks when used by two people full-time. Larger composting may need to be emptied about every 3-4 weeks when used by four people full-time. 

If you do not empty your composting toilet often enough, the composting process could slow down and bad smells could begin.