Guide for bio toilets

In everyday language, "bio toilet" usually refers to a toilet that works without the need of water. Rather than having to use water to flush, the excreta are either composted in the toilet itself or collected, dried and disposed of later. 

The term is not protected and is oftentimes used differently by different people. Two toilet types that are most often referred to are humus toilets and composting toilets. Another term you are likely to come across often is the term "dry toilet". It simply describes any toilet that works without a flush, so it covers both types. 

Contrary to popular belief, the "bio" in "bio toilet" says nothing about certified properties. It is a colloquial label, not a quality seal or an ecolabel. 

The two types that are qualified under the term "bio toilet" mainly differ in whether urine and faeces are collected together or separately. 

Humus toilets collect urine and faeces in one container, where they are composted. Smaller models hold about 20 to 200 litres, which only allows pre-composting. Composting fully inside the toilet needs a container of several hundred litres and takes around 24 months. Because composting produces gases and heat, humus toilets need a ventilation system. Many models also use agitators or heating elements and therefore need a power connection. 

Composting toilets separate urine and faeces from the very first moment. A urine diverter directs urine into a liquids container and faeces into a separate solids container. The solids dry out and can later be composted in a separate composter or disposed of via the normal residual waste. TROBOLO toilets fall under this exact category of toilets. 

Humus toilets and composting toilets share three features: 

• No use of water: They work without a flush, so no drinking water is used or wasted on the toilet. 
• No need for a water or sewage connection: They can be set up anywhere without needing to worry about plumbing, for example in a garden or a van. 
• No use of chemical additives: The toilet works without any chemical toilet fluids. The only necessary additive is litter, which consists of natural byproducts such as sawdust or coconut fibre. 

For comparison: in Germany, a person uses around 122 litres of drinking water per day, of which approximately 33 litres go to flushing the toilet. A toilet without a flush does not require this water and doesn't produce any wastewater from flushing that would otherwise need to be treated at a sewage treatment plant. 

Humus toilets collect urine and faeces together in a shared container, where biological decomposition begins. Naturally occurring microorganisms gradually break down the organic matter, while added litter, such as sawdust or wood shavings, absorbs excess moisture, covers fresh waste and helps maintain an airy structure.

For composting to work effectively, the contents need the right balance of moisture and oxygen. Because urine adds considerable moisture, the material can become too wet and compacted, restricting airflow and causing unpleasant odours. A ventilation system is therefore essential: it helps remove moisture and gases while supplying oxygen to support decomposition. Depending on the design, mechanical mixing or heating may also be used to improve the process, but these features can require electricity.

In smaller humus toilets, the limited container volume generally allows only pre-composting. For complete composting directly inside the toilet, a much larger chamber and a long processing period are needed. The resulting material must be sufficiently decomposed and hygienically safe before it can be handled or used. Depending on the system, further composting in a separate composter may be necessary.

TROBOLO toilets are urine-diverting composting toilets. An integrated urine diverter automatically directs urine and faeces into two separate containers:

1. Urine flows into a liquid container at the front of the toilet.
2. Faeces and toilet paper fall into a solids container at the rear, which is lined with a replaceable inlay.
3. After each bowel movement, a handful of litter is added to cover the solids and absorb residual moisture. 

Separating urine and faeces from the outset helps prevent the formation of unpleasant odours. In particular, it reduces the conditions that lead to ammonia-related smells. The solids also remain drier, making collection and disposal easier.

Depending on the model, the composting toilet can be equipped with an optional natural or electric exhaust system, that helps remove any leftover moisture and odours from the solids container. 

The natural version uses the chimney effect and requires no electricity. The electric version uses a fan with a maximum power consumption of 1.3 watts to create a slight negative pressure and extract air to the outside. Depending on the model and intended use, the collected solids can subsequently be composted in a separate composter or disposed of with the residual waste. 

Due to the similarities in how bio toilets function, they also share some accessories. In addition to toilet paper, both humus and composting toilets use litter. However, composting toilets require considerably less, as urine is collected separately and does not need to be absorbed. Depending on the toilet type, suitable litter and urine containers help make everyday use and handling easier.

For composting toilets, the solids container is another essential component. It collects faeces and toilet paper and can be fitted with a replaceable inlay, making emptying and disposal easier. Inlays are available in conventional plastic or compostable materials, depending on the model and personal preference.

Ventilation is also important, although its purpose differs between toilet types. Humus toilets require a ventilation system to support the composting process and remove moisture and gases. For composting toilets, an exhaust system is optional and primarily helps reduce residual odours by extracting air from the solids container.

Cleaning a bio toilet is generally straightforward and mainly involves wiping the seat and surrounding surfaces with a damp cloth.

Disposal depends on the type of toilet. In smaller humus toilets, the pre-composted contents must be transferred to a larger composter for further decomposition and maturation once the collection container is full. Humus toilets with a sufficiently large integrated composter only need to be emptied once the compost is mature.

In composting toilets, solids and liquids are emptied separately. The solids can be removed together with their inlay and disposed of with household waste, similarly to used nappies or composted in a separate composter where local regulations permit. How often the solids container needs emptying depends on usage and the type of inlay. 

Plastic inlays can generally remain in place until the container is full. Compostable inlays should typically be replaced after about a week, as they begin to break down during use.

Inlays carrying the "OK compost HOME" certification mark, usually displayed on the inlay or its packaging, can be placed in a suitable home composter together with their contents, where local regulations permit. This certification applies to the inlay itself, not automatically to the toilet waste. Inlays certified only for industrial composting under EN 13432 are not suitable for home composting.

Liquids should be emptied into a regular toilet or disposed of in accordance with local requirements. If you want to use collected urine as a garden fertiliser, we recommend checking local regulations before doing so. 

Because bio toilets function with no water or sewage connection, humus and composting toilets are especially practical where there is no plumbing. Humus toilets with a large composter need a fixed place with enough floor space. Compact composting toilets can be set up almost anywhere their size allows. Typical places include: 

• Small gardens and allotments 
• Weekend and holiday homes 
• Tiny houses 
• Mobile homes, vans and boats 
• Dog schools and riding schools 
• Day-care centres 

Naturally, models with an electric exhaust system need a power supply, for example a socket or a solar setup. 

The preceding remarks already illustrate quite well the versatile ways in which bio toilets can be used, nonetheless, the concrete advantages and disadvantages of bio toilets are outlined below:

Advantages

• Waterless: No connection to the sewage system required
• Self-sufficiency: Independence from water and sewage connections guarantees the greatest possible freedom in the choice of location for the bio toilet
• Hygienic: The plastic and wooden seating surfaces allow easy and hygienic cleaning; emptying the solids container is done in a few easy steps
• Odourless or odour-neutral: Litter and exhaust air system reliably reduce odour formation in humus toilets; in composting toilets, odours can even be completely eliminated thanks to the separating and exhaust system
• Free of chemicals: Decomposition of solid and liquid excretions occurs naturally and is not prevented by environmentally harmful substances
• Possible composting: If permitted locally, the dried solids can be composted and later used as soil for ornamental plants; the collected urine can be used as natural fertiliser when mixed with water in a 1:10 ratio

Disadvantages

• Long composting intervals: It usually takes two calendar years before excreta are completely transformed into mature compost soil
• Space-consuming: Humus toilets with integrated composter inevitably require a collection volume of several hundred litres, which takes up a correspondingly large amount of space
• Electricity connection or costs: Some models rely on an electrical exhaust air system and require an appropriate connection. Large composting reactors also require additional electrical accessories, thus increasing the cost balance

"Bio toilet" is a colloquial term, usually for humus toilets and composting toilets. What they have in common is that they work without without a water or sewage connection and without chemicals. 

Which type suits you depends on where you want to use it. Humus toilets compost in the toilet itself but need a lot of space, ventilation and often a power connection. Composting toilets are compact, separate urine and faeces right away, and keep odours low. They are just as suitable for a garden or a van as for use inside your home.