Compost tea questions

jrei at jrei at
Wed Jun 21 23:36:16 EDT 2000

Kevin Chisholm wrote:

> Dear Joel @ Territorial Seed
> Joel Reiten wrote:
> >
> >...del...
> >
> > You first need to make a distinction between high
quality compost tea
> > with vigorous aeration and compost tea produces with
only moderate
aeration or
> > by steeping, they are of great difference in quality.
> It would seem to me that the very high levels of
oxygenation would
> simply duplicate the aerobic sewage treatment process. In
it, most of
> the nutrients are taken out of solution, and are deposited
as a sludge.
> How does the aerobic process maximize the microbes and
nutrients in
> solution without "going too far" and producing cleaned
water and a
> settled sludge?

In 'brewing' this type of tea the compost is held within a
cylinder in the
center of the tank. Bacteria, protozoa, nematodes and some
fungus is
extracted from
the compost and placed in solution. The bacteria then began
to divide.
This is
somewhat analogous to sewage treatment, during the aeration
process, but
that's when
the analogy ends. After about the first hour of the process,
the major
activity is
aerobic bacteria growth and reproduction. The brewing
process continues
approximately 18-20 hours at which point the bacteria have
consumed all
of the
available sugars and division slows. Sewage treatment
requires several
more processes
to complete.

> >
> > To produce compost teas that have a very high level of
> > nearly super- oxygenation needs to occur in the vessel.
This is
achieved with a
> > pump and a specially designed nozzle that was first
designed as a
> > performance oxygenation nozzle for gasoline engine
carburetors in
Europe. By
> forcing the liquid
> > through the nozzle the liquid in broken up and the
maximum amount of
oxygen is
> > added to it. This allows the bacterial to multiply very
quickly. This
is why
> > you load the brewer with such a small amount of compost.
In our case
we use
> > about 2 pounds of compost  per 50 gallon batch.
> If you know the BOD (Biological Oxygen Demand) of the
material, it is
> relatively simple to size the oxygenator system for a
given load. There
> are many "oxygenation technologies" available.....
especially for
> aquaculture. (I once designed a system for oxygenating 4
cubic meters
> per second of sea water, to raise its oxygen content from
6 ppm to 13
> ppm, and strip nitrogen at the same time.)

Yes it is certainly possible to aerate using other systems,
but aeration
pressure nozzles are the quite efficient, relatively simple
and trouble

>  We have never even come close
> > to the numbers of microbes and the results achieved by
using steeping
or forced
> > air with an aquarium pump.
> I miss the point here...could you please clarify?

The point is that one of the main purposes of using compost
is to add
biological like back into the soil to stimulate natural
nutrient cycles.
The more
micro biological life that can be added in the most
efficient way, will
be of most
benefit.. Rapid aerobic brewing is one way to achieve this
because it
will take the
microbes, primarily bacteria, and increase their numbers.
Steeping tea
from manure or
compose only removes the microbiology, very little growth
takes place,
and the longer
the compost or manure is soaked the more of this growth is
which we have
found for the most part to be non-benificial from the stand
point of
natural nutrient cycles or for disease suppression.

> > High quality, finished compost is the key to good growth
in the
brewer. There
> > is indication that vermacompost is superior in the fact
that the
population of
> > microbes seems to be greater and the populations of some
of the
> > microbes seems to be greater leading to better plant
disease control.
> >
> > The molasses and the kelp are food sources for the
bacteria as it is
> > multiplying. The growth of microbes in the brewer is so
great that
> > temperature in the brewer reaches 90F.
> >
> Would not the molasses ferment to ethanol, and then the
ethanol would
> oxidize to vinegar? (This is what easily happens if I
don't air-lock
> aging wine adequately!!) Is the temperature rise perhaps
due to
> oxidation of the  nutrients, rather than growth and
multiplication of
> microbes?

Fermentation is a primarily anaerobic system. No
fermentation takes
place. No, the
rise in temperature is closely correlated to bacterial

> > The matter of dilution is one of preference. The 1:10
ratio brings
the average
> > bacteria count to that of excellent compost. We use it
at 100%
strength in the
> > greenhouse and anywhere from a 50% mix down to the 1:10
ratio in the
>  It is puzzling how diluting the compost by 2 pounds in 50
> pounds) or by a ratio of 1:175, that one could end up with
10 times the
> bacteria count. Could you please explain how this can
happen? Note that
> there is 10 times the concentration, and 175 times the
total mass, so
> that effectively, you are indicating that oxidation of the
> magnifies the microbe count by a factor of 1,750.
> >

Good compost teas have a around a billion bacteria per ml.
steeped in water
has about 1 million bacteria per ml. Compost teas produced
under vigorous
have 5 billion bacteria per ml. Oxidation and the proper
food source will
exponentially grow bacteria.

> I look forward to your helpful inputs.
> Thanks very much
> Kevin Chisholm

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