If you’re considering using a composting toilet, you might well be wondering, “Will it stink?”. This is an obviously understandable question. Now, I love my composting toilet, and I’m a huge advocate for all of the benefits, but there is a reality I should share. If the composting process goes awry, you can get odor. However, the odor isn’t always unbearable, and it can usually be fixed very easily. Let’s delve deeper into understanding why a composting toilet might smell bad, and what you can do about it.
Do composting toilets smell bad? Composting toilets can smell bad, if they are not managed correctly. Usually, this is due to the composting process not working as it should, which can be due to a number of reasons. The problem can usually be fixed by adjusting the conditions to support a healthy composting process. That might be through better separation of liquids, a change to temperature or ventilation, or by adding more organic bulking material. For an immediate fix, you can mask the smell with a fragrance.
Table of Contents
Understanding Why a Composting Toilet Might Smell Bad
How odors are formed in a composting toilet
Odor is actually unusual in a well-performing composting toilet. If everything is going well, you’re unlikely to have any issues. It will be very similar in fact to a regular flushing toilet.
It is when the system is left unmaintained, or when conditions change to a point where the bugs are not happy, that odor and other unpleasant issues occur.
You are effectively managing a biological process down there in the compost pile. You need to make sure the bugs are happy! And whilst they are very resilient and forgiving, if the temperature changes too much, if the moisture becomes too high, or if unfavorable, harsh chemicals are added, the balance might become upset. The strategy therefore is to try to understand what has gone wrong with your composting process and correct it.
When all is working well, your composting toilet will manage the process effectively, turning your deposits into rich compost, which, when fully composted, no longer smell.
The role of urine and solid waste in compost toilet smell
Surprisingly, urine is often more smelly than solid toilet deposits. And if left mixed in the solids, in too high a volume, it can produce a nasty odor. You need some moisture in your compost pile to keep things in balance, but flooding it with urine can cause it to go septic and smell.
To avoid this you can either drain away the ‘leachate’ liquid from the bottom of the compost pile, or you can install a urine separator in the toilet pedestal.
Also, many composting toilets are designed to evaporate away liquids. This requires the correct temperature and ventilation. If your system is designed in this way, make sure that these systems are functioning correctly.
Are some composting toilets less smelly than others?
Modern composting toilets, like urine-diverting toilets, or those with electric heating and ventilation, do effectively lessen the risk of stink. They ensure the correct moisture content in the solid waste and keep the composting process going as required. However, any composting toilet system can effectively manage odor if maintained and used correctly. They really don’t need to be complicated systems.
The key is to keep conditions right for the composting process to occur. This means not overloading it, not flooding it with urine, allowing to vent, keeping the organic bulking material up to it in the correct ratio, and ensuring the temperature is within the right range.
Dealing with your Composting Toilet’s Unpleasant Smell
Emptying your composting toilet properly
Proper disposal is essential when using a composting toilet. It’s crucial to routinely empty the urine canister and solids container to prevent overloading the system and avoid the smell. Follow the manufacturer’s advice in this regard. We have a whole article on this topic that you might want to check out, Composting Toilet Dumping: A Complete Guide to Responsible Emptying and Composting.
Liquids separation to reduce smell
Liquids like urine in the composting process can contribute to the smell. Use a pee separator to take urine away, leaving only solid compostable material in the pile, at the correct moisture content. This can often fix the stink.
If your system doesn’t have a pee separator, retrofitting one might be tricky. You might be able to swap the pedestal for one that separates. Otherwise, you might need to fix or install better drainage from the system.
If moisture levels are too high, a quick solution is to bulk it out with sawdust or leaf litter. This will change the liquid-to-solid ratio and dry things out.
Another option is heating the compost pile to evaporate the liquid. Some systems come with this functionality built in.
Using fireplace ash or lime to reduce smell
If the system becomes too acidic, it may become septic and stop composting as you intend it to. You can get a strong hydrogen sulfide smell. The addition of fireplace ash or lime can increase the pH and neutralize the acidity, therefore bringing the process back into the correct range. Correct pH of the system will minimize any smells.
Fixing poor composting conditions in your composting toilet to reduce stink
If optimal conditions are not maintained, the process slows down, which can cause a smelly toilet. Making a few adjustments can speed up the composting process and get things back on track. This might be fixing the drainage to remove excess liquids, changing the temperature (with a heater or sun), adding more bulking material etc. Over time the system will be happy again and the smell will disappear.
Ventilation and fragrance
Good ventilation can promote a faster composting process, reducing smell bad occurrences. A vent, preferably coupled with a fan, can help. Many composting toilets are designed so that they extract air and gases from within the chamber, sending them up a stack to vent away outside. In doing this, a negative pressure is created on the inside of the compost chamber which slowly draws air in through the lid. Therefore smells cannot come up into the toilet room.
Also, adding pleasant natural scents to the room can mask potential composting toilet smells.
Keeping the lid down
An obvious solution but often overlooked. Make sure the lid is kept down, and you may want a seal between the lid and seat to keep odor in.
Preventing Unpleasant Smells from a Composting Toilet
A healthy composting process for avoiding bad smells
Really the key to all of this is to keep a healthy, happy compost pile. A healthy composting process keeps the stink at bay. With proper solids and liquid separation, correct temperature, and the addition of sawdust or some other bulking material, unpleasant smells can be minimized.
Maintenance requirements for avoiding bad smells
Proper maintenance of your composting toilet will avoid unwanted smells. Composting toilets do take more maintenance than regular toilets, and you must be prepared to manage them correctly for a trouble-free experience. Regular emptying and cleaning of the toilet, including a good wipe down and using a spray bottle filled, with a vinegar and water solution, can keep it odor-free.
Improved Airflow
Good airflow is necessary to keep your toilet from smelling bad. Fans expel air and gases, preventing accumulation which can cause a stink. The more effective the ventilation, the better. If you don’t already have one, consider installing a fan and PVC pipe that expels gases up above the roof. If you’re off the grid, consider a small 12v solar PV which can drive a fan (such as a computer fan) when the sun is shining.
A Final Thought
A well-functioning composting toilet should not have to smell bad. You will barely smell it at all. With proper understanding of the composting process, maintenance, and care, composting toilets can be a smell-free and eco-friendly option for everyone.
FAQs
Q: Does a composting toilet smell bad due to “pee and poo”?
A: Not necessarily. Well-managed composting toilets should not emit a stinky smell. If there is a persistent bad odor, this usually means that something is wrong with the composting process, such as the moist balance being off or the solids chamber not being emptied regularly enough.
Q: Does the urine scale contribute to the odor?
A: Yes, urine scale or dried urine in the toilet unit can generate a strong and unpleasant smell. Regular cleaning of the toilet, especially the urine canister, can prevent this issue.
Q: Can “pee and poo” be decomposed without generating a smell?
A: Composting toilets allow pee and poo to decompose naturally and the resulting solids no longer smell like excrement after adequate composting time. Effective microorganisms play a big part in this decomposition process.
Q: What can be done to prevent the smell?
A:Smelly composting toilets can usually be fixed very easily by adjusting the conditions to support a healthy composting process. That might be through better separation of liquids, a change to temperature or ventilation, or by adding more organic bulking material.
Q: Can you smell anything when the toilet lid is closed?
A: With a well-maintained composting toilet, you should not be able to smell anything when the toilet lid is closed. If there is a smell, there could be a problem with the system such as an issue with the toilet seal and improper composting.
Q: Are composting toilets at home different from camping toilets regarding smell?
A: Both types should not emit a bad smell if maintained properly. However, portable camping toilets are not typically composting toilets and need to be emptied and cleaned more frequently due to their smaller size.
Q: Can condensation inside the canister contribute to the smell?
A: Yes, condensation can lead to increased moisture and therefore a greater smell. Regular emptying of the canister can help control condensation and the resultant smell.
