Frequently Asked Questions
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In a composting toilet feces and toilet paper compost with a "bulking agent" like sawdust cover the poop to create air gaps for aerobic bacteria to break down the material. This process is the same as for a household food scrap compost. Urine can be diverted out of the toilet, but it is not necessary. If urine is included more sawdust is added to soap up excess liquid. Composting toilets are often used in areas with easy access to wood shavings. The finished product is a moist humus similar to garden compost.
In a dry toilet ash or lime mixed with dry soil are added to create a dehydrating environment for breakdown and die off of pathogens. Dry toilets are often used in arid, dry climates where lime and ash are more available than sawdust. Toilet paper can not be added to a dry toilet, it is usually burned or buried. Pathogens typically die off more quickly in the dry, high pH environment of a dry toilet. The finished product can be used as a soil amendment and resembles instant coffee.
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Pharmaceuticals are being found at an increasing rate in fresh water, including the drinking water of many major cities. The following is an excerpt from the report: Urine Diversion: One Step Towards Sustainable Sanitation by EcoSanRes.
There are research projects going on to investigate the environmental effect of pharmaceuticals in urine. By far the majority of all pharmaceutical substances are derived from nature, even if many are synthetically produced, and they are thus found and degraded in natural environments with a diverse microbial activity. This has been verified in ordinary wastewater treatment plants, where the degradation of pharmaceutical substances improved when the retention time was prolonged from a number of hours to a number of days. Urine and faecal fertilizers are mixed into the active topsoil, which has a microbial community just as diverse and active as that in wastewater treatment plants, and the substances are retained for months in the topsoil. This means that there is plenty of time for the microbes to degrade any pharmaceutical substances and that risks associated with them are small.
Concerning both hormones and pharmaceutical substances, it thus seems far better to recycle urine and faeces to arable land than to flush them into recipient waters. Since the aquatic systems have never before been exposed to mammal hormones in large quantities, it is not surprising that the sex development of fish and reptiles is disturbed when they are exposed to wastewater effluent. Furthermore, the retention time of the wastewater in the treatment plants is far too short for many pharmaceutical substances to degrade and recipient waters are also usually connected to water sources.
There are many indications that the possible risk from pharmaceutical substances in the agricultural system is small and far smaller than the risks associated with the present system. One such indication is that in many countries the human consumption of pharmaceuticals is small compared to that by domestic animals, as in most countries most commercial feeds contain antibiotic substances, added as growth promoters. Furthermore, the human use of pharmaceutical substances is small compared to the amount of pesticides (insecticides, fungicides, bactericides and herbicides) used in agriculture, which are just as biologically active as pharmaceutical substances.
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Urine should be used like a nitrogen based fertilizer, apply it to the roots of nitrogen demanding crops or plants. You can either dilute it one part urine to 3-5 parts water, or just water the plant with fresh water after you have applied the urine. Remember to alternate between plants and not overfertilizer with urine. We usually alternate between plants being fertilized so each plants receives urine once every two to three weeks. If you have a small yard and don't need all the urine for fertilizer it can be added to the food or yard waste composting bin and will provide extra nitrogen to the compost.