[USCC] aerobic composting, definitiion

[Chaney, Rufus]

Dear John and USCCers:

I think we all recognize the point you raise here and have raised before. Successful management is an "art" and must deal with the issues you raise.

The heart of the discussion is whether composting is "aerobic" or "anaerobic" in nature. During the composting process, O2 level will fall during periods of rapid microbial action, and between aeration events. From beginning to ending, the process generally becomes more and more aerobic as the BOD is metabolized. But if the process goes anaerobic, it generates a huge malodor and requires careful management to obtain aerobic status and proper management to become aerobically stabilized. The fact that low O2 levels are found in the center of compost piles during the middle of the composting process is simply "composting" under aerobic conditions. Too high aeration cools excessively, or enough aeration replaces O2, removes CO2 and water, and cools appropriately. 

But the process and product are "aerobic".

Please focus on the big picture. Composting should never be used to describe an anaerobic process.

Regards,

Rufus Chaney
Beltsville, MD

-----Original Message-----
From: compost-bounces at mailman.cloudnet.com [mailto:compost-bounces at mailman.cloudnet.com] On Behalf Of John A. Crockett
Sent: Wednesday, March 11, 2009 11:56 AM
To: U.S. Composting Council listserve
Subject: [USCC] aerobic composting, definitiion

There is a lot of discussion on anaerobic and aerobic.

What is the specific definition of aerobic composting in terms of the oxygen
level in the compost?  Is it 5% oxygen, 10%, 15%?  What CO2 levels are still
acceptable under the definition of "aerobic"?  OR, is there no such
definition?

I strive for 1 - 2% CO2 in the off-gas, and I base that on assaying the
active bacteria population, and the fact that we've gotten our best
populations of active bacteria when the CO2 in the off-gas was less than 4%.

We've also had many cases where in the early days of the process, we've
sustained temperatures > 150°F with a rate of aeration > 25 times the volume
of the compost, in fresh air, every hour, in order to hold the CO2 within
those limits.  

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

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