(This is an article I published in German in the magazine "Kritische Ökologie", slightly modified.)
An experience that not everybody knows yet: You enter a toilet and there is a smell of forest soil. This way every use of the toilet gets a pleasant experience ...
We are used to considering our excrements something unpleasant, disgusting, nearly a taboo theme. We like to simply wash them away with a lot of water. Then they get into the sewage treatment plant where they are waste that has to be done away with. What happens there, is beyond our interest because it is far away – out of the eyes, out of the mind.
This is an attitude that tends to dominate all our way of thinking: We humans often regard ourselves as disturbing troublemakers within nature, we think, we do not produce beauty and usefulness but rubbish that we want to get rid of, that we want to through away. But where is "away"? In a limited system like the Earth there is no "away". The sewage partly gets in the waters, including the ground water, it leads to hypertrophisation (too many nutrients) and robs the water oxygen what threatens the water fauna. Moreover pathogens can spread out that way. And to wash away the human valuables we even use up a considerable part of our drinking water.
A fascinating alternative to this is the composting toilet which is a lot more than only an outhouse or netty. It is based on a completely different attitude towards ourselves and our excrements: They are valuable and usable, a fact that also makes our bodies appear more worthy. Everywhere people speak of recycling these days. And exactly where nature has been planning circulation since the beginning of all ages, we should start with it: with organic substances. We produce excrements and throw for example sawdust on it which leads to the odour mentioned in the beginning. Hardly anyone would consider the result unhygienic. In areas without trees there can be found alternatives to sawdust, for example soil. For sake of this additive the whole mixture can compost very well. (Still there are reports of composting toilets that work without additives.) Small animals like woodlice, ants and centipedes bustle about and so do a good job that the material gets mixed and decomposes. The compost recieved free of charge can be used instead of chemical fertilizer that has been produced and transported with the use of much energy and costs money. In addition it provides humus.
A legitimate question may arise: Is this fertilizer really hygienic? Are there no pathogens in it which spread out with the compost when used? This is a reason why a good composting process is crucial. Prejudices that state human manure (or "humanure") should never be used as a fertilizer, are a result of wrong uses. In biological-dynamical (anthroposophical, that is) agriculture even today this opinion is held true; it refers to the knowledge of 1924 and today is outdated. It is true for fresh human excrements, the so-called night soil, which should not be used for fertilization, especially not for foods. Otherwise there would really be the risk of pathogens spreading about. First the night soil has to be transformed by microorganisms. And that is exactly what a composting toilet serves for: In the container below the seat the mixture of excrements, toilet paper and sawdust is well mixed by small beings and biochemically transformed during several months or a few years.
Still, on Ibiza it was a traditional use to dry the excrements and use them as a fertilizer for vegetables, especially nitrophytes of course.
There are different mixtures of manure. Some people like to separate the urine from the excrements, this is possible yet not necessary. Organic kitchen-waste can be thrown into the composting toilet or can be composted separately. The decision can be taken according to one's needs and local experiences.
In areas with scarce water (like Ibiza) a water closet with the use of drinking water is problematic anyway. A composting toilet on the other hand gets along with no water use at all. Only for washing one's hands afterwards is a bit of water needed. For this purpose the rain water might be used that falls on the toilet roof; it can be caught in a container to be ready for use. After use the same water can still serve for watering plants in the garden.
Those who know the protection of the environment only from moralising suggestions, may tend to believe that this all is mere theory and difficultly can be put in practice. But - the beauty of the composting toilet lies in the fact that it has been used for millennia. The Wikipedia has the keyword "composting toilet" in quite a few languages with reports from practical experiences and a historical view. The fact that the public shows a growing interest in this topic, can be seen in that Joseph Jenkins' "Humanure Handbook" quickly became a bestseller.
It's curious that on Ibiza just in the hippie meeting centre "Casita Verde" there are two composting toilets which work very well.
Joseph Jenkins: The Humanure Handbook. A Guide to composting human manure. Grove City, PA 2005, 3rd edition.