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

Natural separation of excreta

Composting toilets support the natural separation of human excreta and consistently maintain this.

In this way, the excreta can be composted in a targeted manner and returned to nature. In other words, following nature's example. This article takes a closer look at the composting of solids and the possibilities for urine conversion.

Nowadays, faeces are mainly disposed of via the sewage system and finally treated in sewage treatment plants. This process is very costly.

In addition, a lot of sewage sludge is produced in the sewage systems.
Without a connection to the sewage system, you have a better solution with a dry composting toilet.

Ultimately, bacteria and microorganisms can optimally fulfil their task by separating the faeces and initiate conversion and decomposition processes.

However, the separation of solids and liquids is important here, as the respective bacteria need a different environment to be able to work properly.

Where to put the urine?

Disposal via the sewage system

The simplest option is to dispose of it via the sewage system, especially if you are connected to it. Ultimately, any wastewater pipe, such as the old toilet or sink, can be used.

However, you should be aware of the build-up of urine scale due to the mixing of urine with water. This must be cleaned thoroughly on a regular basis. Proven household remedies for the toilet are vinegar essence and baking soda.

Fertiliser in the garden

If you have a garden, you can use diluted urine as fertiliser. The plants will be happy about the nitrogen, potassium and magnesium it contains.

For one thing, the mixing ratio should be suitable: 1:10 to 1:20, depending on the plants to which it is applied. There are weak, medium and strong growers.

It is also important to use it sparingly. Used in this way, urine can be a valuable fertiliser in the garden. Some garden lovers call it "gold water".

Alternative new ideas for urine use - constructed wetlands and urine diversion via clay walls

Constructed wetlands are plants covered with vegetation in which wastewater is treated. The plants in hydroponics, microorganisms, wastewater components and the filter substrate purify the wastewater.

You can read more about this on Wikipedia. Such constructed wetlands have many advantages and are very natural.

They are also available in many different versions. However, it is worth mentioning that in most municipalities this special technology is subject to compulsory connection to the public sewage system. Good, detailed advice from experts is highly recommended.

A further alternative is to trickle the urine through a clay wall. However, this technique is almost extinct.

In Yemen, this technique is still practised today. Urine is run over a clay wall, where it dries up quite quickly and the remaining nitrates, especially saltpetre, are removed.

These are either burnt or reused as fertiliser. In the past, there was still the profession of saltpetre worker, whose job was to scrape the saltpetre from the clay walls.

This was then sold on to fertiliser and munitions factories. In the course of the further development of man and chemistry, the need disappeared and with it the clay walls. Incidentally, odours do not arise here due to the rapid drying.¹

Dealing with faeces

The solids can be composted well via your own outdoor compost, via third-party central composting collection points or via closed compost bins. In the following, I will go into more detail about the individual options.

Kompostierung einer Trocken-Trenn-Toilette

Composting on the compost heap

It is advisable to add some litter material while the dry composting toilet is still in use to support drying and aeration.

By adding straw, sawdust, garden waste or bark mulch, the compost has a good aeration possibility.

I recommend reading my article "Bedding for a dry composting toilet". Here I describe the individual materThis provides an ideal habitat for small soil animals and microorganisms that carry out the transformation process.

By further adding mixed soil with ash, the composting process is set in motion more quickly.

Composting process

I would like to present the composting process in a somewhat abbreviated form:

For one year, the contents of the container are collected in a heap. At each emptying, make sure that the faeces are well mixed and fairly dry.

After the year, the pile is turned over so that the microorganisms and soil organisms can carry out their task of decomposition.

In order to work their way through, they need rest. It should be noted that the turned heap should be stacked quite steeply and high in order to promote the rotting process through better aeration.

The emptying of the fresh solids thus begins on a new site.

At the end of another year, you move both heaps separately and start building a third one.

Proceed in this way year after year so as not to disturb each rotting phase. Each pile is in a different phase. Bringing them together disturbs the respective process.

Compost becomes humus

After a short rotting period of two to three years, the heap is hygienically harmless but still quite acidic and still contains organic mass.

This raw humus mass is not yet optimal for incorporation into the soil, as the high nitrogen content, for example, can flatten the soil fertility zone.

This means that soil organisms and roots only remain in the upper part of the soil. In the long run, the soil structure deteriorates as a result.

With compost that has been worked through for a long time, the soil can extend its fertility into deeper and deeper regions. Among other things, this improves erosion resistance.

According to Central European conditions, gardeners recommend a rotting time of three to four years.

Of course, this requires patience. The individual heaps naturally become smaller and smaller until finally a small amount of mineral humus substance remains.

This can then be added in fine quantities to improve the soil. Often, however, the older heaps no longer have such a mass, so that a mixture of the three- and four-year-old is recommended.

Composting in a collection container or thermal composter

If there is no possibility to create a common garden compost with several piles, you can also use a thermal composter for the solids.

But here, too, the use of several thermal composters is strongly recommended. In order for valuable humus to develop, it should be given the time it needs to go through the individual decomposition phases.

Therefore, regrouping is also recommended here. For composting in such a thermo-composter, the addition of humus or compost starter is necessary to introduce a larger quantity of micro-organisms and soil organisms that drive the composting process. A heat-safe environment is important for such compost types.

Important notes - Potential pathogens and parasites

Long-term composting has the positive side effect that parasites die off over this period.

The same applies to pathogenic organisms and undesirable bacteria. They are degraded either in one of the first phases (hot rotting) or ultimately during long-term composting. They can only survive for a certain time in an undesirable environment.

Therefore, you should follow the recommendations of the three- to four-year rotting phase. This way, the resulting humus will find a good use.

¹ https://www.hofgut-maxau.de/mediapool/92/926875/data/Eigene_Dateien_2/dissjoerglange.pdf