> Date: Thu, 11 May 2000 07:29:50 -0400
> From: David Drexler <firstname.lastname@example.org>
> Subject: anaerobic vs aerobic
> Could someone please tell me the basic differences between anaerobic and
> aerobic digestion. Why are these systems not in use to solve the
> manures and waste problem in the US?
> David D
Both of these systems have been in existence since the first
one celled organisms croaked billions of years ago. They
have always been used whether by nature or mankind.
Decomposition is either aerobic, anaerobic or a mix of the
Waste water treatment plants commonly use a combination of
One of the most common ways to process waste is to use a
process called activated sludge. It is primarily an aerobic
Another process commonly that has been in use for a long
time is the "digester" and is a anaerobic process.
As you can see the technology is readily available and
proven but these processes are costly energy users. They
require air, water and sludge pumps in the tens to hundreds
of horsepower to operate properly in the small spaces modern
waste water treatment plants operate.
If the circulation or recirculation and aeration
capabilities on these systems are lowered then they cannot
operate well in the small spaces they currently occupy. In
other words the higher the power or energy input the less
space you need but there is a point of diminishing returns.
Lagoon systems are a mixed mode aerobic/anaerobic system
that uses various micro and macro organisms in a quiescent
environment to handle the sewage (whatever it may consist
of). It is energy cheap but requires huge areas as it has no
man made energy input so relies on passive nature processes
to get the job done. These are common in small communities
If you want to use these processes to convert poop you must
remember one must have energy inputs which could bankrupt
farms already under cheap competition or have HUGE lagoons
to minimize stink since they are partially an anaerobic
The stench is the anaerobe critters doing their thing which
also release hydrogen sulfide which smells bad and methane
which you don't think much of.
Many waste water plants will typically burn off the methane
produced using it to heat the buildings in the plant or for
other uses requiring heat. The boilers are beat up pretty
good by the dirty methane these digesters produce.
There actually is no waste problem. Waste is doing very well
There is a DISPOSAL problem that regulatory agencies are
trying to control but in some cases their mindlessness is
making things worse.
For instance here on our farm we were looking into using
waste for our vermiculture operation. Our Colorado state law
used to be such that anything brought on a farm and used on
a farm to grow stuff that left the farm was not considered
waste but manure or fertilizer. A simple but cool law!!
There have been many occurrences that have formed our non
recycling farm policy but I will limit it to one story.
At a recycling seminar I attended in 1999 there were around
40 people. I and a speaker were the only NON government
employees there. It kinda bugged me that other farmers and
business people were absent but I figured it was the low
profit margins and didn't consider that a reason to not do
As the seminar went on I was impressed by the local efforts
put out by the local governments and volunteers to recycle
and such. The private sector speaker was most inspiring and
I felt ready to jump on the band wagon.
Then the health department representative spoke. He was
interested in power, control, regulation and enforcement.
His message stunk of BIG government protecting the people
from every possible problem at my expense. I literally felt
I inquired as to the status of the manure/fertilizer farm
law and he said it would have to be replaced. I asked a few
more questions and after learning of the extent I would have
to get licensed, inspected, regulated, and basically be a
unpaid servant to the government I decided not to pursue off
farm manure, compost or other inputs.
It is now obvious to me why there were 38 government people
and 2 of us private sector types in that meeting.
So originally when we started this farm we had the desire to
have to bring stuff onto our farm to use for fertilizer,
mulch, manure, etc. We have moved on from that idea as it is
a BAD business decision due to regulatory considerations.
Now you know one farmers reason.
Marc S. Nameth
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