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Scatalogical Reflections from a Vermicomposting Privy |
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Written by Administrator
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Sunday, 11 September 2005 |
by David Lee Hoffman, from our issue #8
REFLECTIONS - Shit Happens! And Happens! And Happens! Tons and tons of
it every moment, but we just don't talk about it, the topic is too
taboo. Actually, it's just as common and natural as the food we eat,
but, once food enters the mouth and is savored, masticated and
digested, we think its gastronomic and utilitarian functions are
complete. What we don't often realize is that when this food has
completely passed through our bodies, the fecal matter we produce still
has the potential to be a food source - not for pigs and street dogs,
but as important sustenance necessary to maintain healthy soil.
 For thousands of years, since the dawn of agriculture, night soil
(human excrement) and animal manures were collected as valuable
resources. This practice allowed an important cycle to be completed
connecting the link for sustainable farming practices that are so
important to the survival of life. Human fecal matter was respected. It
had worth. It fertilized fields, adding precious nitrogen to the soil,
and it aided the process of thermophilic decomposition of organic
wastes. Farmers of old Japan would vie with one another in building the
most inviting outhouses along thoroughfares to entice the travelers to
drop in for a good bowel movement. In China it was traded as a precious
commodity.
Although modern societies have gone a long way from those natural
practices, some individuals have returned and are proving that
composting human excrement can be simple and safe. The key words to
remember are containment and isolation. If we're going to pursue this
process, we've got to do so in a careful manner. Raw excrement does
have the potential to spread disease. Thus we do have to take
precaution to prevent physical contact. Intestinal parasites, diarrhea,
dysentery, hepatitis, typhoid fever, cholera, and polio, all have the
potential to be transmitted through contact with raw feces. However, it
is important to know that all parasites and pathogens, outside of a
susceptible host, are destroyed by time and temperature.
There has been research in the area of thermophilic decomposition of
fecal matter in composting privies. There is no argument that a
properly managed pile of human excrement can reach temperatures
necessary for destruction of harmful pathogens. The thermal death
points of common intestinal parasites and viral or infectious
contagions are well below temperatures achieved in a balanced pile.
Many are destroyed in minutes. The problem is that to achieve these
optimum conditions is both labor and management intensive. Small piles
do not heat up sufficiently until a critical size is reached, about a
cubic yard. Furthermore, this doesn't happen with small daily
contributions. Large masses need to be created to produce the bulk
necessary to activate thermophylic conditions. Piles need to be turned
regularly and monitored to be certain all parts of the pile are exposed
to sufficient heat for an adequate amount of time. Tools in contact
with the pile need special treatment, too. Commercial composting
privies often supply external heat and incorporate rotating chambers to
accomplish mixing and prevent cold spots. These systems work well but
consume energy.
THE VERMICOMPOSTING PRIVY
My own system, which is an example of pathogen destruction through
biological digestion and isolation through time, has been in operation
more than five years. Below the floor, the unit consists of two
separate chambers, roughly 4' x 4' x 6' high. The 12" thick brick walls
have a 2" layer of rigid insulation at their core. The floor is
concrete and slopes to the front at a 20 degree angle to facilitate
drainage of excess liquid. This collects in an enclosed non-ferrous
perforated metal pipe to which a ball-valve-controlled spigot is
attached. The inside of the two chambers are coated with a thick layer
of calcium aluminate cement (50:50 cement/fine sand mix plus 10% fire
clay) for acid resistance and long life. The 2' redwood access doors
have 6" x 18" ventilation screens to allow fresh air into the chambers.
A No. 30 mesh screen is used to keep out all flying pests. The entire
structure is built with recycled brick.
Like the Japanese farmers of old, I tried to build a clean, well-lit,
inviting place. A sign hangs to remind prospective contributors, "NO
DEPOSIT - NO RETURN". Nevertheless, some visitors are shocked by its
primitive simplicity.
Daily deposits are made from the room above into one of the two
chambers below. The other chamber continues as a normal vermicomposting
pile with kitchen scraps and yard trimmings being added, but no fecal
contributions are allowed. At first we alternated chambers every six
months. This was certainly sufficient time for thorough composting of
the contents. There was nothing unpleasant when I shoveled out the
contents into an open-air holding area. It looked and smelled like fine
rich soil, and it didn't attract flies. For one year it was further
worked by the worms and other soil organisms and finally it was added
as a mulch around our fruit trees. The following year we switched to a
yearly alternating cycle. This meant it was two years minimum before it
was used on the land.
Deposits are made through two 8" x 20" openings, which when not in use
are sealed with snug-fitting lids. A small solar powered ventilator
mounted in the ceiling brings in fresh air, although when the system is
operating properly, no offensive odors are generated by it. The only
fly problem occurred in the beginning when the 8" ceramic vent pipe,
which runs up through the roof, was capped for rain but not screened
for flies. This oversight admitted some uninvited guests. They
discovered a very fertile breeding ground in the lower chamber and in a
short time we had a horrendous fly situation. This was remedied by
screening the rain cap and applying about five cups of clean wood ash
and bone flour, which I make in my wood burning stove, to the pile
below. The elevated pH and gritty texture created an inhospitable
environment for the fly maggot population. They disappeared as rapidly
as they had come without the use of anything toxic that could have
effected the healthy redworm and microorganism colonies.
Bad smells were generated a few times in the early days. Invariably
this was due to excess moisture caused by weekly contributions of
several hundred pounds of kitchen scraps from the local organic health
food store. Reducing this to an occasional contribution remedied that
problem.
In the "stomach" of this system is a diverse community of micro and
macro organisms interacting in a natural food chain. The most obvious
creatures are the sow bugs, whose appearance has given rise to a share
of squeamish comments. But their benefit to the composting system
cannot be denied as they are great scavengers, and, when they die,
their bodies provide needed calcium for the redworm population. The
most notable organisms in my present system, of course, are the
redworms, Eisenia foetida and Lumbricus rubellis. They're in it for the
long run, mixing, digesting, and aerating the contents. In addition to
being the backbone of the system they are also indicators, and the
results, of a good balanced system. Not so obvious, but also important
are the myriad of tiny organisms and microorganisms. As long as this
diverse community is fed a healthy balanced diet, it will flourish.
And, with time, all potentially harmful pathogens and parasites are
destroyed.
Perhaps from my years of living in Asia, I am most comfortable
defecating in a squatting position. The human body seems to be best
designed to perform this function in that position. Also, as in the
Asian tradition, my preference for personal hygiene is to use water
instead of toilet paper. (I applaud Dr. Helen Caldicott, for standing
up in public and praising the virtues of this habit!) For those who
prefer otherwise toilet paper is provided. Though I accept its habitual
use in our culture, in my opinion, I feel it is a waste of trees and
can be unhealthy due to trace amounts of highly toxic dioxins that are
present even in unbleached, recycled paper products. Although this adds
a couple of cups of water with each use, this has never been a problem,
even in the winter when the rate of evaporation is much slower.
The system operates on nature's basic principle of biological
decomposition in which a balanced environment is necessary for carefree
operation. When balanced, there is no turning of the pile - the worms
do all that work. There is no maintenance involved, other than draining
off excess liquid, should it become necessary, a function that can
easily be set up to operate automatically. Any excess liquid is simply
run back through the system after adding a bucket or two of some dry
carbonaceous material such as leaves or sawdust. These materials are
always on hand as a handful of them should be added to the pile after
every deposit. Once a week, or so, I sprinkle a blend of wood ash,
oyster shell flour , bone meal, powdered charcoal and granite dust on
the pile below. These serve as extra odor control as well as food for
the organisms. It also ensures that there will be extra mineral content
in the finished product. All of these items I am able to make here or
procure free. Another item I find to be beneficial for a healthy
balanced system is to add a shovel or two of topsoil every couple of
weeks.
To sum up my attitude about my unusual system for waste utilization, it
is said that "waste is not waste 'til it's wasted". I'd like to add,
"Shit isn't waste if it's composted."
(Ed. Note -Having visited David's brick vermicomposting privy, I can
attest not only to its successful functioning but also to the sublimity
of the room in which one is invited to squat. My only regret is that,
at that time, I had no contribution to make.) |
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Last Updated ( Sunday, 18 September 2005 )
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