Dear Anandji...
I just understood that it is called byphasic. Yes, the first tank is for
stirring purpose and for simplification of mixing all types of input.
Thanks for the idea. I will feed the food waste directly.
I will use as small as possible of water tank (may be max 25 liter) for
the fecal matter.
Namaste,
Deepak
Message: 2
Date: Sun, 20 May 2012 21:26:02 +0800
From: Anand Karve<[email protected]>
To: [email protected], For Discussion of Anaerobic Digestion
<[email protected]>
Subject: Re: [Digestion] mixed waste AD
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Dear Deepak,
If I have understood you correctly, what you are planning to do is to have
a biphasic digestion system, in which the first tank would be for stirring
the material with water in an open tank, exposed to air, and to allow the
overflow from this tank to enter into the anaerobic digester. The quantity
of biogas generated by anaerobic digestion is directly proportional to the
digestibility of the feedstock. Human food consisting of sugar, starch,
protein and fats has high digestibility, so that 1 kg (dry weight) of any
of the above substances would yield about 1 kg biogas, if it is introduced
directly into an anaerobic digester. In the case of green leaves, the
midribs and veins, consisting of lignin, cannot be digested by the
methanogens, so that the digestible matter constitutes only about half the
dry weight. You would therefore have to introduce about 2 kg (dry weight)
of leaves into the anaerobic digester to produce 1 kg biogas. In
comparison to the anaerobic microbes, the aerobic micro-organisms are much
more efficient in breaking down biomass. Therefore, stirring the biomass
with water in an open tank would oxidise the easy-to-digest material into
carbon dioxide and water. If you spent too much time on stirring, only the
difficult-to-digest material would enter the anaerobic digester and your
biogas yield would be rather low. My advice would be to introduce food
waste and kitchen waste directly into the anaerobic digester and subject
only the fecal matter to mixing under aerobic conditions.
Yours
A.D.Karve
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