[compost_tea] Re: Air Required + Measuring

From: Kirk Leonard <kirk_at_oregonatural.com>
Date: Wed, 8 Oct 2003 10:01:30 -0700

In compost_tea_at_yahoogroups.com, Robert Norsen <bnbrew_at_y...> wrote:
> We just fiished 9 ACTt runs in the SFI lab 3 identical
machines, identical quntities of compost, identical nutrients. We
recorded DO2 readings near the low points of the O2 use curve of
3.2, 7.8, 5.7 Not a constant variation but a typical variation.
>
> Our conclusion up to this point is that O2 demand is extremely
variable depending on compost and/or nutrients. There are so many
variables including the compost itself there may be only one way to
select O2 input SYTEM :
> . PUT IN MUCH MORE AIR THAN IS NORMALLY NEEDED MOST OF THE TIME <
Are you yelling now, Bob? How do we know "how much air is normally needed"
if we haven't tested for differences in air volume, which you apparently
didn't do in the tests you mention? I appreciate the quest for a
predictable recipe, but I'm talking about differences in tea quality
resulting from air volumes, all else held constant. I agree variations in
compost and nutrients are likely to change air requirements but how do we
know where to start? We're just guessing until we've done some testing at
different air volumes.

Dennis asks a real good question, too. Are you sampling DO in the tank or
using grab samples? In-tank sampling could account for the variability in
and of itself, seems to me. I'm not saying in-tank testing isn't useful,
just that getting a bead on DO differences among machines probably requires
grab sampling and measurement out-of-tank. Also, if the three measures you
state are from three different runs (times), it's quite possible the
differences are due to barometric/atmospheric pressure differences during
the runs. And as I recall from Kevin's description, you were testing with
different composts, right? That info would be interesting to hear along
with DO diffs.

I disagree that the measuring method I suggested is "an all-day affair," and
in my experience yours is definitely not "really exact" -- in the process of
getting the bag onto the tank, there is no way to keep air out. Freeboard
air is irrelevant but air in the bag is not. Further, how are you gonna use
a plastic kitchen bag on a big KIS, or better yet, a WormGold unit, or your
own 250 gallon unit? No can do with any bag I've ever seen. If you use a
hefty enough piece of plastic for the tank cover you can re-use it (on any
number of machines if you cut the sheet big enough, too), in which case the
method I suggest would be quite quick and easy, as only measuring bag needs
prep. And how do you account for pump phase differences?

I can't find your original method description. Would you re-post, perhaps
with a little more detail? Maybe I did something wrong.

-- Kirk




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Received on Thu Oct 09 2003 - 21:34:46 EDT

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