Feedback on Night Soil: Composting Human Waste

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PHOTO: FOTOLIA/DMITRY NAUMOV
Composting human waste — aka "Night Soil" — can be easily done in a way that also controls any problems with flies or odor. 

In MOTHER EARTH NEWS Edith Little asked for information about
using yeast in a privy to decompose and deodorize feces or
“night soil.” I don’t know of any yeast that will serve
this purpose, but I do know that composting human waste can be
done very nicely. There will be little objectionable
odor … much less than from the average privy where waste
is allowed to pile up and putrefy, creating unhealthy
conditions. Flies will also be eliminated and the resulting
fertilizer will be of very high quality: an odorless,
crumbly black gold for the garden.

In order to compost effectively and efficiently, night soil
must be mixed with material that is high in cellulose or
carbon. I find that sawdust, wood chips, pine needles or
old leaves–in a ratio of four or five parts sawdust
or whatever to one part excrement by volume–seem to
work best. Straw or hay isn’t satisfactory, for it tends to
pack down and is difficult to turn over later on.

The sawdust should be dumped down the hole of the privy
after each use to completely cover your latest “gift to the
earth”. Use more if necessary, to insure that flies cannot
get down into the night soil to lay their eggs. The mixture
should be kept damp but not sopping wet.

After a period of time, as the pile builds up in volume, it
will begin to heat. At this point the material should be
turned over with a long-handled pitchfork every two or
three days, depending on how much the privy is used. This
will keep the pile cookin’ by supplying air to the aerobic
bacteria responsible for the composting process … and
will also insure that any stray fly larvae on the surface
of the mass get dug into the hot center and destroyed.

The heat is caused by the work of beneficial microorganisms
which break down the night soil-sawdust mixture. If
conditions are right, the temperature will be high enough
(at least 150° F for about 24 hours) to render the
compost completely free of any disease-causing bacteria. As
an added safeguard, I would not use the fertilizer on
plants that will be eaten raw until the dressing has aged
for at least one year.

It would be advantageous if the privy were designed to
allow easy access to the composting chamber for turning and
removal of the contents. The facility could be as simple as
a tarp strung over a three-foot-deep pit in the ground …
all that’s needed is something to keep the pile from
getting too wet.

After the pit is full the privy should be moved to another
location … or, if this is impractical, the compost dug
out and re-piled elsewhere. You should continue to mix and
water the material until it’s cool to the touch. At this
time you could throw in some red wriggler earthworms (which
can be obtained from your local bait dealer or ordered
through the classified section of Gardening and
Farming
magazine) to further insure that the end
product will be nothing like what you started with. The
heap should then be covered with a tarp or sheet of plastic
to prevent leaching, and allowed to age for one year
(unless the fertilizer is to be used on fruit trees or
crops that will be thoroughly cooked, in which case it
could be spread as is).

In MOTHER EARTH NEWS Milton Wend suggests using
night soil which has merely been treated with hydrated
lime. I myself would be wary of fertilizing crops with
human waste unless it had heated up to 150° F in a
controlled composting operation and/or aged for at least
one year buried in a pit. The Chinese used to get around this precaution by never
eating any vegetables raw (see Farmers of Forty
Centuries
by F. H. King).

Further and more detailed information on composting night
soil can be found in the book Composting by Harold
Gotoos. The
author also gives a nice set of plans for a community-size
methane generator.

Bruce Martin
Ponca, Arkansas


An innovation that I’ve seen lately–and that I would
surely include in the building/remodeling of a
privy–is the use of a vent pipe running from the vent
or waste area to above the roof. It keeps the air inside
the privy fresh and successfully eliminates the inside odor
… even when nothing else is used.

Harold & Grace Brown
Yarmouth, Maine

You’re right, Harold and Grace … and the article,
“Privies, Old and New” contains cutaway drawings of two versions of outhouses
built with such vents.–MOTHER EARTH NEWS.

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