[USCC] how much air do the microbes need?

[John A. Crockett]

How much fresh air / oxygen do the microbes need, to work efficiently?  Is
passive aeration able to deliver enough air via convection, in windrow
composting?  Could you work without oxygen?  I've read that if people have
over 2½% CO2, that they get splitting headaches.  That would be about 18.5%
oxygen.  Are we trying to optimize the working conditions for the microbial
master composters?

Back in 1996-1998 we did a lot of cross section profile monitoring of
passively aerated windrows, monitoring oxygen, CO2 and temperature, and some
of that data is on our website for those who want it.

Over the past month I have personally done 41 air flow rate tests on our
compost research silos, where we strive to hold the CO2 in the off-gas
between 1 - 2%, as measured using a Fyrite CO2 meter.  The AVERAGE air flow
rate, over 41 tests done over the past 30 days, was 21.2 times the volume of
the compost, in fresh air, every hour.  And frequently we're getting
temperatures above 150°F.

Granted, we're dealing with food residuals, and we're often shredding to
less than 1/4", often less than 1/8" particle size.

Is it possible that some of the things we're doing results in higher oxygen
consumption?  Is it possible that we're getting higher populations of active
bacteria and fungi when we don't deprive the microbial master composters of
oxygen?

Our compost research silo work has taught us that the rate of air flow has
to be adjusted, and that oxygen or CO2 in the off-gas ought to be the
primary decision criteria, with some other elements woven in.

Working Together to Create a Sustainable Environment,
John A. Crockett, a.k.a. Dr. Mike Robe
Mother Nature's Farms, Inc.
(845) 225-7763
http://www.magicsoil.com/
jac at magicsoil.com