A composting toilet disposes of waste without water, with minimal odor, and in an environmentally friendly way. Instead of wasting resources, it transforms waste into nutrient-rich humus through biological decomposition, thus closing the nutrient cycle.
Especially in tiny houses, mobile homes, gardens and remote areas, it serves as a sustainable alternative to conventional toilets.
But how exactly does it work? What advantages does it offer, and what challenges need to be considered? Is it also suitable for installation in a motorhome? This article provides the most important answers.
What is a composting toilet?
A composting toilet is a dry sanitation system that collects human excrement such as feces and urine, which is then transformed into nutrient-rich humus through biological decomposition. Bacteria, fungi, worms, and composting insects carry out the breakdown in the composting process, while bedding materials such as sawdust or coconut fibers absorb moisture.
A ventilation system, also called an exhaust system, prevents odor formation by supporting the separation of solids and urine and promoting aerobic composting.
Since a composting toilet operates without water, it does not require a connection to the sewer system or wastewater treatment plant. It is an ecological alternative to conventional toilets or lavatories.
The recycling of nutrients, as practiced in the circular economy, contributes to sustainability and environmental friendliness. Instead of wasting resources, it transforms waste into valuable compost.
Particularly sophisticated models, such as the BioTioo compost variant, use an agitator in the solids container that mixes the excrement with plant fibers, accelerates drying and initiates pre-composting.
The term compost has an ambiguous meaning, as it refers both to the end product of decomposition and to the entire biological process.
The functionality of the composting toilet is based on the principle of the circular economy, in which organic materials are recycled instead of being considered waste.
Disposal is straightforward. The urine is collected in a separate tank and can easily be emptied into a toilet or drain, while the dried solids can be disposed of in biodegradable bags in the regular trash or on the compost heap.
How does a composting toilet work?
The functioning of a composting toilet as a sanitary disposal system is based on the biological conversion of human excrement such as feces and urine into compost.
Depending on the design, pre-composting or complete decomposition into humus takes place. The crucial factor is the capacity of the collection container, which varies between 20 and 200 liters. Smaller models store excrement for short-term storage, while larger systems allow for more advanced decomposition within the container.
The process begins with the addition of bedding material, such as coconut fibers, in the solid area, which absorbs up to six times its weight in moisture and promotes drying.
Advanced models utilize a mechanical agitator: After each use, the mixture of solids and fibers is stirred using a crank or motor. This reduces moisture, initiates pre-composting, and decreases the volume of excrement.
Heating elements or a fan are integrated to accelerate the fermentation process. This not only reduces the moisture but also decreases the volume of the excrement.
The urine is collected in a separate tank with or without an odor trap and can be easily emptied.
Once a certain stage of maturity is reached, the contents are emptied and processed further on a compost heap or at a central collection point. There, the final composting takes place, creating a closed nutrient cycle that returns organic nutrients to the environment.
How does a composting toilet differ from a toilet?
A composting toilet differs from a conventional toilet in its waterless operation and the biological decomposition process of the excrement.
While a flush toilet directs excrement directly into the sewer system, a composting toilet uses bedding materials such as bark mulch, coconut fibers, or sawdust to regulate moisture and absorb odors. The absence of a flush reduces water consumption, eliminates the need for wastewater treatment, and saves costs in the long run.
The seating position and use remain almost identical, but the absence of water requires active handling of excrement. Unlike a simple separating toilet, where urine and solids are collected separately but the solids are merely covered with litter without any actual pre-composting, a composting toilet relies on a more intensive process.
With a traditional separating toilet, decomposition remains limited because the bedding material primarily binds odors by covering the excrement and only regulates surface moisture. A composting toilet, on the other hand, often uses an agitator that mixes the solids with the plant fibers, thereby accelerating drying and initiating pre-composting directly in the container.
This reduces the volume of excrement and promotes biodegradation, whereas a separating toilet without an agitator requires more bedding and the solids are stored more or less unchanged.
A flush toilet relies on a piped water and sewage system, while a composting toilet functions independently. This independence from infrastructure makes the composting toilet ideal for remote areas, garden sheds, or sustainable housing projects.
The finished compost can be used as fertilizer for ornamental plants, thus returning the nutrients to the natural cycle.
How do composting toilets differ from dry separating toilets?
Composting toilets and dry toilets (TTT) differ primarily in their method of waste processing and space requirements. While a composting toilet biologically decomposes excrement directly within the system over months or years, a dry toilet collects solids separately without immediate composting taking place.
Both systems use bedding material to minimize odors, but a ventilation system is recommended for a composting toilet to regulate moisture and promote biological decomposition. Otherwise, condensation can form in the camper during temperature fluctuations, hindering drying and exacerbating odors. A dry separating toilet doesn't necessarily need this fan, as the solids are only temporarily stored and later disposed of.
Urine is also collected separately in both systems to prevent the solids container from becoming over-wetted. In some composting toilets, the urine is even evaporated to reduce the liquid volume, while in dry toilets it is often used as liquid fertilizer.
Another difference lies in the space required. Since composting toilets need a larger container for long-term decomposition, they are often more voluminous than dry toilets, which manage with more compact collection containers.
What accessories are needed for a composting toilet?
A composting toilet requires specific accessories to ensure its functionality and hygiene. The most important component is the bedding material, which absorbs moisture, reduces odors, and accelerates composting. Suitable materials include bark mulch, sawdust, or other cellulose-based materials that act as organic binders.
In practice, however, almost all composting toilet manufacturers use coconut bricks, also called humus bricks, because other materials tend to clump and not absorb enough moisture, which would impair the efficiency of the system.
Additionally, a composting toilet requires a lid for the liquid container to regulate evaporation and minimize unpleasant odors. However, this lid is only necessary for some manufacturers whose models do not have an integrated odor trap, while there are models with an odor trap that do not require an additional lid.
A cleaning kit containing citric acid maintains the components, removes deposits, and preserves the system's longevity. Models with an electric exhaust system or agitator require a power connection to support air circulation and optimize the decomposition process.
Which toilet paper is suitable for a composting toilet?
For a composting toilet, biodegradable, environmentally friendly toilet paper is best, as it doesn't interfere with the composting process. However, models like the BioTioo can easily use ordinary household toilet paper, simplifying daily life and eliminating the need for additional purchases.
Other systems often require special paper to ensure optimal decomposition. Bamboo toilet paper offers a sustainable alternative, as bamboo regenerates quickly, requires little water, and also decomposes rapidly. To shorten the decomposition time, single- or double-ply paper should be used, as thicker versions decompose more slowly.
Chemically treated papers containing dyes or fragrances should be avoided, as they can harm the microorganisms in the compost.
How does the emptying and disposal of composting toilets work?
Depending on the model, emptying and disposal of a composting toilet is done either through external composting or via an integrated system for converting organic waste. In models without a built-in composter, the collected excrement, along with bedding material, is transferred to a composting facility or compost heap, where it remains for at least 24 months before it is fully humified.
A closed compost bin accelerates the decomposition process, while an open compost heap can be slowed down by weather conditions. Adding organic waste from the household and garden promotes microbiological activity and improves the structure of the compost material. Since rainwater can impair composting, a protective cover is recommended to maintain the moisture balance.
In composting toilets with an integrated composter, the finished compost can be removed directly after a minimum resting period of two years and used as a natural fertilizer for ornamental plants, trees and shrubs.
For composting toilet models that are frequently used for motorhomes, pre-composting takes place in the solids container, which can be removed and then disposed of directly in the residual waste.
How often does a composting toilet need to be emptied?
The emptying frequency of a composting toilet varies depending on the model, container size, and intensity of use. In a two-person household, the solids container needs to be emptied on average every 2 to 6 weeks, depending on the capacity and the type of pre-composting. To ensure efficient decomposition, the container should be emptied no later than when it is three-quarters full.
The urine container, however, requires more frequent emptying, as limescale and unpleasant odors can form during prolonged storage. Depending on the model, emptying every 1 to 3 days is recommended.
How do you clean a composting toilet?
Cleaning a composting toilet requires minimal effort, as it functions without a water flush and no deposits form in the drain. Unlike a conventional toilet, which requires chemical cleaning agents, simply wiping the seat with a damp cloth is sufficient. Toilet brushes or harsh cleaners are unnecessary, as no limescale or dirt residue is produced by water.
The external maintenance of the toilet differs little from that of a conventional sanitary system. The composter itself requires no manual cleaning, as it serves as a fermentation and decomposition system, and the biological breakdown process occurs automatically. The interior of the composting toilet can be cleaned with mild, biodegradable cleaning agents to maintain hygiene.
For the urine tank, it is recommended to add some washing powder or a dishwasher tablet and let it soak overnight with water to prevent limescale buildup and dissolve deposits.
Where are composting toilets used?
Composting toilets are used in locations without a water connection, as they function independently of the sewage system. They are suitable for indoor and outdoor use, with the specific model determining the ideal location. Toilets with an integrated composter require more space, while models with a small collection container offer more flexible positioning.
They are a particularly practical solution in gardens, on golf courses, riding stables, and in dog training schools, where conventional sanitary systems are often not feasible. They also enable sustainable waste disposal in forest kindergartens without causing soil contamination. In tiny houses, vacation homes, and weekend cottages, they offer an environmentally friendly alternative to the classic flush toilet.
Advantages of composting toilets
Composting toilets offer a sustainable and resource-saving alternative to conventional toilets. Their waterless operation, self-sufficient use, and environmentally friendly properties make them particularly attractive for various applications.
They reduce water consumption, minimize wastewater treatment and support the circular economy by returning nutrients to the soil.
The following are the main advantages of a composting toilet.
- Waterless operation
- Self-sufficient use
- Environmental friendliness
- No chemical additives
- Low-odor use
- Nutrient recycling
- Low operating costs
- Less maintenance than chemical toilets
- Sustainable alternative to traditional toilets
- Versatile applications
1. Waterless operation
Composting toilets do not require flushing water, making them independent of water connections and sewage systems. This saves drinking water, reduces wastewater pollution, and makes the toilets usable even in regions with water scarcity. Since no flushing is necessary, there is also no polluted wastewater that requires costly treatment in sewage plants.
2. Self-sufficient use
Because they are independent of water and sewage systems, composting toilets can be installed almost anywhere. They are ideal for off-grid homes, mountain cabins, campsites, or RVs. Many models operate completely without electricity, while others require minimal power for ventilation systems.
3. Environmental friendliness
Composting toilets promote a circular economy by transforming organic waste into nutrient-rich compost. This eliminates the production of chemical wastewater that could enter the environment. At the same time, their waterless operation protects natural water resources and prevents the overloading of wastewater treatment plants.
4. No chemical additives
Unlike chemical toilets, composting toilets function purely biologically. They require no chemical additives for odor neutralization or fecal decomposition. This ensures environmentally friendly disposal and guarantees that the resulting compost can be used as fertilizer without harmful residues.
5. Low-odor use
Thanks to bedding materials like sawdust, bark mulch, or coconut fibers, moisture and odors are effectively absorbed. An integrated exhaust system ensures continuous ventilation, further reducing odors. The aerobic decomposition process also prevents the formation of foul gases, which often occur in conventional wastewater systems.
6. Nutrient recycling
Composting toilets transform human excrement into nutrient-rich humus, which can be used as a natural fertilizer for ornamental plants, trees, and shrubs. This closes the nutrient cycle, instead of treating excrement as waste.
7. Low operating costs
Since composting toilets don't use water and don't require a sewer system, there are no water or wastewater fees. Furthermore, there are no ongoing costs for chemicals like with other portable toilet systems. High-quality composting toilets also have a long lifespan and are designed for minimal maintenance.
8. Less maintenance than chemical toilets
Unlike chemical camping toilets, there's no wastewater tank that needs to be emptied or refilled with chemicals regularly. Cleaning is easier, as there are no deposits or limescale residues from flushing water. Most models only require regular refilling of bedding material and occasional emptying of the collection container.
9. Sustainable alternative to traditional toilets
While conventional toilets consume dozens of liters of drinking water daily for flushing, composting toilets operate completely waterless. They reduce resource consumption, avoid chemical pollution, and contribute to a sustainable lifestyle. They are an ideal solution, especially in eco-friendly building projects or self-sufficient households.
10. Versatile applications
Composting toilets are not only suitable for private use, but also for public parks, construction sites, mountain cabins, or temporary events. Their simple installation and minimal environmental requirements make them a practical solution in numerous areas. They are also a popular choice for people who want to live independently of conventional infrastructure, especially in motorhomes, tiny houses, or garden sheds.
Disadvantages of composting toilets
Although composting toilets offer many ecological and practical advantages, there are some challenges that should be considered when using them.
Composting requires time and space, and depending on the model, additional maintenance and accessories may be necessary. Furthermore, they are not ideal for all living situations, especially in rented apartments or urban environments.
The following overview details the main disadvantages of composting toilets.
- Long composting time
- Space requirements
- Interim storage required
- Disposal is more complex than with toilets.
- Special accessories required
- Electrical components in some models
- Higher maintenance costs than flush toilets
- Restricted use in rented apartments
1. Long composting time
The process of complete decomposition into compost can take up to 24 months. This means that the feces must be stored for an extended period before they are fully usable. Those who prefer quick disposal might consider this a disadvantage.
Therefore, almost all manufacturers speak of pre-composting within the system, which should not be confused with complete composting – it merely serves for drying and initial decomposition, while the final humus formation takes place externally.
2. Space requirements
Compared to conventional separating toilets, composting toilets with an integrated composter require a larger collection volume. This can pose a challenge in small living spaces, tiny houses, or motorhomes.
However, a separate container for bedding is not necessary, as it is usually only added once and remains in the solids container. While some models are large and bulky, the BioTioo, for example, is compact and smaller compared to other systems, thus reducing its space requirements.
3. Interim storage required
Since complete composting takes time, the collected solids must be temporarily stored in the toilet after pre-composting until the final humus formation.
Depending on the frequency of use, this may require regular emptying of the collection container and a well-organized composting area in the garden at home or a central collection point to complete the process if you wish to use it as compost – alternatively, you can simply dispose of it in the organic waste bin or residual waste.
4. More complex disposal than with toilets
While flush toilets discharge wastewater directly, a composting toilet requires manual emptying of the collection container. This can be unfamiliar or unpleasant for some users. Furthermore, the compost must be properly processed before it can be used as fertilizer.
5. Special accessories required
To make composting efficient and hygienic, bedding such as sawdust, bark mulch or coconut fibers is needed, with coconut fibers being used in particular in the BioTioo and other composting toilets for motorhomes.
The fibers are already available as ready-to-use bricks that are easy to handle. Depending on the model, a ventilation system or a compost accelerator may also be required to optimize the decomposition process.
6. Electrical components in some models
High-quality composting toilets often use electric fans, agitators, or heating elements to improve moisture control and the composting process. These components consume electricity, which can complicate their use in energy-independent systems or in regions without a reliable power supply.
7. Higher maintenance costs than flush toilets
Unlike conventional toilets, which only require a water flush, composting toilets need to be emptied and refilled regularly. The moisture level must be monitored to ensure optimal decomposition. Furthermore, improper use can lead to unpleasant odors.
To minimize maintenance, the BioTioo, for example, features a patented design that optimizes the composting process with the agitator, allowing all dry waste to simply fall out.
This eliminates the need to clean the solids container. Refilling with litter is also unnecessary, as the remaining bacteria act as a compost starter for the next use.
8. Restricted use in rented apartments
In rented apartments or urban residential areas, the use of a composting toilet is often difficult, as it requires a suitable disposal location for the compost.
Without a private garden or collection point, long-term use becomes more complicated. Furthermore, structural modifications may not be permitted. However, the BioTioo, for example, has a UTA (Ultra-Direct Drainage Device) that allows urine to be directed into the drain at home without the need for a urine tank.
Can a composting toilet be easily installed in a motorhome?
Yes, a composting toilet can easily be installed in a motorhome; it simply requires careful planning and professional installation. First, the existing chemical toilet must be removed, which is straightforward in most vehicle models thanks to its standard screw-in mounting. The new toilet should be positioned so that there is sufficient space for the toilet seat and controls.
An essential part of the installation is the exhaust system, which must be routed to the outside via a hose to minimize odors and ensure air circulation.
If the toilet has an electric ventilation system, a power supply is required, which can usually be provided via the existing connection of the chemical toilet. The BioTioo 2.0 has not one, but three connections for the fan and can be flexibly mounted to the floor and wall thanks to ten pre-lasered holes.
For installation, suitable mounting materials such as screws, wall plugs, and a drill are required. Unlike a permanently installed flush toilet, a composting toilet in a motorhome offers the advantage of being usable independently of fresh water and wastewater systems, thus enabling greater self-sufficiency while traveling on the road.
Does a composting toilet also work in cold temperatures?
A composting toilet also works in cold temperatures, although with certain limitations in the decomposition process. Since microbiological activity is highly dependent on the ambient temperature, composting slows down considerably at temperatures below 13°C and can even come to a temporary standstill during frost. However, as soon as it gets warmer, the biological decomposition process resumes.
Regardless of the temperature, the fan's drying function remains active, ensuring uninterrupted use. Furthermore, BioTioo composting toilets are highly frost-resistant, thanks to their stainless steel back mechanism that functions flawlessly at all temperatures and the use of high-quality polypropylene C.
Additional insulation generally helps to retain heat indoors and increase comfort, especially in unheated rooms or mobile applications.
