Replacing the classic WC with sustainable toilets

We’ve been brought up to think that the water closet is the most modern and hygienic solution to treating our human waste.  “Correct, until the waste comes out of the house, after which we consider that the rest of it is not our problem. Only it is our problem,” pointed out Flemming Abrahamsen, one of the pioneers of ecological building in the North, who introduced modern composting toilets in Denmark. By mixing feces and urine with clean drinking water, we contribute to wasting water, one of our most precious resources. This is an absurdity, as human waste is a precious source of nutrients which could be put back into the food chain and used as fertilizer, closing the loop from food to excrement to fertilizer to crops and back to food.

Indeed, the waste from water toilets represents 90% of the individual household’s environmental pollution. And with humans becoming increasingly aware that clean water is less and less available, reconsidering the way we treat our human waste could prove to be a solution to water shortages, health and environmental problems. (An average person defecates some seven pounds per day. This amounts to a little over a tonne of feces per year.) With a flush toilet using as much as 100,000 liters of water a year even before industry sewerage costs, it is worth looking into simple and sustainable solutions to an otherwise very energy-intensive business.

Dry compost toilets, separating toilets and the Aquatron system offer more sustainable alternatives to the otherwise wasteful classic water closet.

Long live the compost toilet!

According to Abrahamson, the only right thing to do is to compost wastes and to retain and separate urine and feces. The biggest problem is that we try to lead urine and feces out through pipes and into the waterways, and to him, this is a catastrophe. Compost toilets use little or no water (‘micro-flush toilets’ use about .5 liters of water per use, compared to traditional toilets, which use up to 13 liters per flush) and treat toilet wastes on-site for reuse as valuable compost. They range from simple twin chamber designs to advanced systems with rotating systems, temperature and moisture probes and electronic control systems.

Initial costs vary widely, but when compared to the price of a septic system installation, a composting toilet system is anywhere from 25-75% less expensive, depending on your location. For example, some new septic installations in Ontario, Canada can run in excess of C$20,000 (about 13 000 euros). Envirolet.com sells composting toilets starting at around 2000 euros, with shipping cost of 149 euros in Europe.

jyttePortable compost toilets are available as well. In Denmark, they are available for about 25 euros. Jytte Abildstrøm, a Danish actress, is leading a promotion campaign for the cause (left). More information can be received in English by writing to toiletja@riddersalen.dk

The true cost savings from transforming waste into compost come in the long term, with the reduced water use costs, non-existent sewage costs, and the ability to produce valuable nutrient humus.

The widescale use of composting toilets would be very beneficial to the environment. Reduced water use would minimise storage and piping impacts, elimination of sewage would reduce nutrient flows into river and oceans and subsequent rejuvenation of marine systems.

Cities could become fertilizer factories instead of nutrient sinks, reducing environmental problems associated with manufacture of fertilizers.

Source separating toilets

Unlike ordinary toilets, where both urine and feces are mixed with potable water and then the greywater (which is all the water coming out from the house from dish washing, laundry and bathing), a source separating toilet keeps the water free from unnecessary pollution. Actually, this is the easiest way to obtain clean water. Just avoid polluting it!

Source separating toilets should not be confused with composting toilets which actually mix urine and feces, as well as other things, and compost it all. 

Because of the large difference in volume and other properties between urine and feces, they should be kept separate, ant treated as the different things they actually are. Urine-separating toilets have a small ‘dam wall’ in the front of the bowl to collect urine.  From there, urine flows to a storage container.  After six months of storage the urine is sprayed on or injected into agricultural land.  A further advantage of source separation is that the resulting greywater can be designed to contain either high or low levels of nutrients in accordance with the end use, or nutrients can be recovered from the greywater before it goes to a land application.

Source separating toilets occur in two principal forms, the dry and the wet.

In the dry type, urine and feces are never mixed, but the urine is flushed with about 2 deciliters of water after each usage in order to avoid crystallisation in the pipes. 
Feces are collected in a mini-composting chamber, in which compost worms might be supplied for a better sanitation and decrease of the volume. After half a year of worm composting, the volume is diminished to about half, and all pathogenic organisms have vanished.

separating toilet

A separating toilet

An unexpected advantage with this type of toilet is that the toilet room becomes free of the odors common in an ordinary toilet room. This is because the air is sucked out from the composting chamber by a small fan to prevent odors. This also clears the toilet room!

The wet type of source separating toilet also separate the urine, but feces are mixed with a significant amount of water for the transport of the material. Ideally, it should be collected in a tank together with e.g. burnt lime for hygienization. In some cases, feces are separated from the transport water by a passive centrifugation. The transport water is subsequently hygienized or just discarded.

aquatron systemThe Aquatron system, for its part, is a wet composting system receiving only blackwater (sewage containing fecal matter).  Solids and water separate in the Aquatron.  Solids fall into a container below and are digested by worms before being recycled back to the land.  The water spins off to join the household greywater for treatment. (Aquatron systems range from 1710 to 4250 euros, excluding shipping costs.)

Information sources:

http://www.pollutionissues.co.uk/building-compost-toilet.html

http://www.aquatron.se/

http://www.holon.se/folke/projects/vatpark/Septoa_en.shtml

composttoilet.org

Innovations from Scandinavia, a paper by Sarah West

http://en.wikipedia.org/wiki/Composting_toilet

envirolet.com

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