[permaculture] worm troubles, probably not!

Kelly Slocum kelly at bonterra.net
Sun Dec 21 15:15:06 EST 2003

~From: "Chuck & Linda" <clearned at bminet.com>
~Subject: [permaculture] worm troubles

~My concern is with venting what I call the "Vermiculture Based
~Unsaturated Aerobic Bio Filter"  I will be flushing my toilets through
~VBUABF. ........  My problem is I live in brrrrrr Wisconsin. The VBUABF
is going to ~hang out in the greenhouse in an insulated container, this
is good as worms like to
~be in a temp range of 68F to 80F(just like us!)  However all toilets
need to
~be vented as the air is displaced when the waste enters the filter
~Venting indoors requires me to run a vent stack to the sky. So here
lies my
~problem 0 degree temperatures dropping down ontop of the worms. {snip}

First, keep in mind that a vent implies movement of air is in your
favor, moving out of the stack, not down the stack into the bin.  Air
movement in such a system as yours is away from the worms, not toward
them.  Conductive cooling is not going to have a significant impact
since air is an insulator.  Warm air in the VBUABF will move up the pipe
and block cold air from moving down into the unit, or at the least will
significantly warm any air that penetrates to the worm area, largely
mitigating the concern.

I would be concerned that use of a flap might not meet code requirements
for your venting system, but I am no expert in the area of building code
and am simply voicing a concern, not commenting from any direct

Worms, however, are my area of study, and one of the greatest
misconceptions surrounding the concept of vermiprocessing is the idea
that the system is readily impacted by cold temperatures and requires
supplemental heating or extraordinary measures to protect it from cold.
The majority of mid to large scale systems being used have greater
challenges related to cooling rather than heating, even in northern
areas of the US, the UK, even Norway.

If yours is a low mass system and IF cold air was moving down the vent
stack then it could have an impact, but it is by no means a given that
it will have sufficient impact to inhibit the effectiveness of your
system.  As has already been suggested, biological activity in the
VBUABF would likely offset the cold, coupled with the fact that the OM
in the system is a heat sink that will buffer rapid temperature changes.
If the system has or can be built with sufficient mass of OM, whether
raw or as finished worm castings, you can dramatically decrease the
impact ambient temperatures can have on the system.  Were you to find
that there was a cooling issue as a result of the stack you might
consider removing the insulation from the tank, taking advantage of the
warm air in the greenhouse which is likely to be a more stabilizing
factor than the cold air will be a temperature de-stabilizer.

In a system like the one you're proposing you do want to optimize worm
activity, but a temperature drop of a few degrees below the worm's
optimum range (were that to in fact be a result of the vent, which is
unlikely) rarely demonstrates a measurable impact.  The types of worms
that can be effectively used in vermiprocessing do not go into
hibernation-like states, rather, they simply slow their activity as
their environment becomes less favorable.  Redworms (Eisenia fetida),
the species most commonly used in vermicomposting systems in north
America, will continue to process significant volumes of organic matter
at temps as low as 48° F, though certainly not as aggressively as they
will in their optimum range.  They are not killed until temps drop to
below 38° F.  

Kelly Slocum
Chief Science Officer, Vice President
Bon Terra, Inc.
phone 360.253.5465
fax 360.253.5466
email kelly at bonterra.net

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