Cool composting of humanure
hit the stage, most of the systems in practice were cool composting
toilets. In contrast to Jenkins' thermophilic composting system
(which I'll discuss in Thursday's post), these cool composting systems
relied on time to kill off any pathogens in the humanure.
In general, leaving a
pile of humanure to compost for two years is a sufficient safety margin
even if the pile doesn't heat up at all, although roundworm eggs can
survive for up to ten years under these conditions. If you apply
composted humanure under the mulch around ornamentals or fruit trees,
though, this issue may not matter.
The Clivus Multrum is
probably the best known of the cool composting systems, and most of the
other designs work similarly. Jenkins recommends designing a cool
composting toilet with at least two chambers so you can close off one
after filling and let the humanure age for a couple of years before
removing the compost. When starting a new chamber, fill it about halfway with an
absorbent, high carbon material, then keep more of the
sawdust on hand to drop down the hole after each use. A
chimney-pipe-type ventilation system will pull any smells up above
nose-level, and leachate can be collected in a five gallon bucket of
sawdust that is tossed back down the hole at intervals.
Despite the problem with
using humanure compost from this type of toilet on food crops, it does
have a major advantage --- simplicity. Unlike Jenkins' system,
there's little regular maintenance required beyond finding sawdust, and
the compost is high quality after the extended aging period.
I'd be curious to hear
from anyone who's using a cool composting system like this. What
design did you use (or what brand did you buy)? How has it worked
out for you? Do you have additional pros and cons to add to this
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