domingo, 20 de octubre de 2013

A Free Minimalist UDDT (part 2)


“Conventional wisdom” or fecophobia (the irrational fear of feces) may lead people to have the following doubts about this system:

Couldn’t the fecal pathogens get out through the woven cloth of the sack?

Aside from hookworm larvae, fecal pathogens do not actively move anywhere and just wait passively to get washed into someone’s drinking water, brushed onto someone’s unwashed hands before they eat, or carried by flies to someone else’s food. These are the risks of open defecation, with fecal pathogens set loose in the environment. Liquids do not flow out of these sacks, given the dry cover material we add after each use, the separation of the urine, and the protection against the rain. The permeability of the woven cloth is actually a positive thing, since this allows humidity to evaporate out and oxygen to filter in (without smell or flies coming or going), so the feces can decompose normally, with the pathogens dying off at an exponential rate. See an example of letting feces decompose in these woven sacks in this video.

As shown in this graph from the Humanure Handbook by Joseph Jenkins, fecal coliform bacteria die in the soil at an exponential rate.

Getting back to the hookworm larvae, they only travel through moist sandy or loamy soil (not clay), so some sticks or stones may be placed under the sack when it is placed under that bridge, and wood ash (which is alkaline) may also be placed on, around, and under the sacks. Furthermore, hookworms are not usually life-threatening, nor are they terribly common, with “only” up to some 740 million persons infected in the world, mostly in Africa and Southeast Asia. It is reasonably easy to check if people have them (using a microscope) and to wipe them out with chemicals or with natural alternatives, such as papaya seeds. Plus we should always remember that hookworm larvae can only be in the feces if the users have these worms. Pathogens cannot come out of nowhere, and, in the case of hookworms, the biggest factor is dogs practicing open defecation and the larvae crawling into people’s feet. (If you do not know what hookworms look like, see this article in the Examiner. Hookworms do not just eat people’s food, but instead their blood. They were clearly the inspiration for the creature in the movie Alien.)

Can we be absolutely sure that all the pathogens will die and that no one could possibly ever get sick via this system?

No. Someone could come along and open the sack before it is time, without reading the tag, but any system can go wrong if not used right. What we can be sure about is that all the fecal pathogens are still alive and kicking in people’s fresh feces that might otherwise go straight into the environment. We also know that these pathogens die off at an exponential rate as feces decompose. The important thing is to keep these nasties jailed up while this is happening and every day of containment is a victory in the war against disease. Essentially all of these pathogens are anaerobes adapted to live in the absence of oxygen, in the aqueous habitat inside our guts, and there is only a certain amount of time they can hang on in a dry, oxygenated substrate before infecting the next person. Given this situation, the most persistent fecal pathogens have evolved desiccation-resistant packaging, like the amoebic cyst and the shell of the Ascaris egg, but even these can only protect them for a certain amount of time.

A key factor is the rambunctious and relentless nature of the microbes in rich organic soil, eating everything that does not eat them first. Most pathogenic microbes would be easy prey to soil organisms and it has been shown that fecal bacteria die-off faster in species-rich soil, as I recommend using here, optimally with the reuse of finished compost as cover material, with exactly the microbes that broke down the feces of the previous cycle, and which are not human pathogens.
Schönning and Stenström (2004) recommend storing the feces, with an ample amount of wood ash or mineral lime for over 2 years in the Temperate Zone and 1 year in the Tropics. Personally, I think this is overcautious, especially in the biodiverse, warm Tropics, but these detention times can easily be applied if there is enough space and it makes people feel more comfortable. These times refer to the most persistent fecal pathogens, which are the eggs of the Ascaris Giant Roundworm, and all the really dangerous microbial pathogens are wiped out in less than three months. We have done trials to look for Ascaris eggs in our fecal compost, here in Amazonian Ecuador, and have yet to find any beyond four months of decomposition. More trials need to be done and a simpler, more conclusive protocol that mostly only requires a microscope needs to be developed. And even I store the feces for over a year, for more peace of mind of all the users.

No one wants to go on record recommending a detention time that may potentially allow someone to get sick, and this is especially the case with governmental and international organizations. I am nonetheless willing to go out on this limb, given that the worst alternative is to continue with the currently abundant cases of open defecation, raw sewage going straight into so many rivers and bays, and 2.6 billion people in the world that do not have any sort of decent toilet. And, if over time, we find that we should modify these suggested detention times (longer or shorter), we can do so.

Aren’t we supposed to store urine for a number of months to sanitize it before applying it on the soil?

This concern is due to the possibility that feces may have contaminated the urine through people using the UDDTs improperly or having accidents … and this is very unlikely with this “bare bones UDDT”, in which the user holds the urinal right where it needs to be. If an accident were to happen, the user could dump the urine in a hole in the ground and cover it up, instead of spreading it on the surface of the soil. In places where there is the Bilharzia parasite, Schistosoma haematobium, urine should be spread on the soil far from lakes and rivers, so that this parasite cannot get to the freshwater snails it needs to infect in order to continue its life cycle.

Won’t some animal, like a dog or a rat, tear open the sack and spread this dangerous material around?

Experience has shown that they do not, especially if we are using soil as a cover material, in particular that special recycled soil. There have been a couple of cases of mischievous dogs, but only when pure sawdust was being used as the cover material. Soil and finished compost are also among the best filters for odors.

Fecophobia aside, other important questions can arise:

Why should we protect the sacks from the sun?   
Wouldn’t the solar rays help to kill the pathogens?

Yes, they would, but the ultraviolet light also destroys the polypropylene plastic strands of the sacks. Solar ovens that take this into account would be a good idea (and we can be much more patient about baking feces for sanitation than about baking lunch for our urgent hunger). According to the following graph, we only need to achieve 65°C for an hour to kill all of the fecal pathogens, and this is much easier than the 100°C required to boil water. One time, a student and I made a simple solar oven from recycled materials, and we apparently got to above 80° C, because the PET plastic Coke bottle got deformed and the Ascaris eggs held within were also seen under the microscope to be deformed and almost certainly dead.

A graph showing the time necessary for various human fecal pathogens to die at different temperatures, from Feachem, R.G., Bradley, D.J., Garelick, H. and Mara, D.D. 1983. Sanitation and Disease – Health aspects of excreta and waste water management. John Wiley and Sons, Chichester, UK (as reproduced in Schönning and Stenström 2004). For example, all pathogens die within one hour at 65° C, or within a month at 45° C.

What if we aren’t quite so broke and want something nicer?

You can do it. If your soil is fairly dry and absorbent and never gets flooded, think about making an ArborLoo, which is a lightweight outhouse that gets placed on one and another one-meter-deep holes where trees later get planted, like this one we made from mostly recycled materials. Remember to add a cup of soil, dry leaves or ashes with each use. If you do not have room to plant an infinite number of trees, you can plant vegetables, like pumpkins, and dig a new hole in the same spot after at least two years.

Also, check out the Simple UDDTs I published in Sustainable Sanitation Practice and various other models on my blog, some of which have beautiful ceramic floors set into thin ferrocement that only needs a half a sack of cement.  And set up a TippyTap to wash your hands.

 What about all the billions of people in the world who wash their back sides with water?

I have been thinking about all the billions of “washers” in the world, who use water for anal cleansing, and how they could use this Free UDDT … and have come up with the following solution. A second Ecological Urinal could be made and marked “Anal and Hand Washwater”, which would be laid on the ground, or propped nearly on the ground, to catch this water. (The lip on this urinal can be bigger to prevent this dirty water from coming out, and two sticks in the ground can prevent it from rolling.) A TippyTap could provide this water, such that the user can step on its pedal to acquire water for washing, without touching the vessel or contaminating its contents. After anal cleansing, the user can stand the urinal up and continue washing his or her hands.

(A TippyTap is a plastic bottle hung on a pole, with another stick on a string that one steps on to tip it and receive a stream of water through a hole in the bottle that was made with a red-hot nail. Standard versions can be seen at and a version that fills automatically with the rain can be seen at )

This little bit of blackwater could be poured into a narrow hole in the ground (a “soak pit”), like a post hole, which could be filled with stones, especially if there is a tendency for the walls to cave in. One could also put a plank as a lid to keep flies and smells from coming and going. If the site has really high groundwater or flooding, some kind of Constructed Wetland of plants would be called for to purify this wastewater.

And if we want to sit …?

You can build a bench, as can be seen on my blog, but I do want to remind you that squatting is the most natural position for defecation (which everyone used for millions of years) therefore:
  • there is less constipation,
  • there are fewer hemorrhoids,
  • it is more hygienic (since genitals do not touch anything),
  • it is more accessible for small children, and
  • the evacuation is more complete.
It is also usually easier and more economical to build for squatting, plus there is better separation of the urine.

Where could this go?

By using this minimalist do-it-yourself toilet, people can not only resolve this sanitary problem themselves immediately, but they can also demonstrate to governments, foundations, and others that they understand and embrace the concept and practice of Urine-diverting Dry Toilets. Many planners and decision-makers would discard this option as a utopian dream that could never be feasible, but in reality local citizens are often much more practical, proactive and down-to-earth than their “leaders”. Once people demonstrate that they can properly manage this bare-bones UDDT, governments and foundations would be much more confident in building fancier, permanent units for these same users. Too many UDDTs have been built and given to the users, with everyone simply hoping that they will use them correctly, and then they are abandoned or misused, because the users were not adequately prepared and convinced of the system.

In fact, this simple toilet could be used as a test for these users to confirm their spot on the list of permanent and elegant UDDTs to be built. After a week of use, someone could visit to see how they have been used, and this would put pressure on them to actually understand and use the toilet and to actually use it properly, since no one would want to be crossed off the list for being messy or not being able to follow instructions.

This design can thus be considered a low but solid rung in the ladder of increasingly user-friendly UDDTs. With it, those 2.6 billion could quickly have a toilet, maybe with some creative redistribution of these plastic “wastes”, especially considering that, since these polypropylene sacks are protected from the damaging rays of the sun, they can be used again and again, year after year. This toilet is accessible to anyone in the world who can rescue a few selected things out of the trash and has a clear decision to keep the environment cleaner and more productive.
If you have any questions or suggestions about this simple toilet, please let me know. I also invite you to read more about the current problems of sanitation in this 
interview and more about Urine-diverting Dry Toilets in this interview.

 Keep water clean 
by keeping sh*t dirty.