[Gasification] [Digestion] Karve connecting Biochar and Biogas

[David]

Paul,

On 10/7/2011 5:41 PM, Paul Harris wrote:
> G'day All,
>
> David House's book "The biogas handbook" has a bit about carbon and charcoal and he does not seem to expect any assistance, possibly inhibition. I guess a lot depends on how the carbon is prepared and what the substrate may be.

Appreciate the mention, Paul, and I hope you are well.

I assume you are referring to pp. 65-66, where some work done in 1971 
by Laura and Idnani (Increased Production of Biogas from Cowdung by 
Adding Other Agricultural Waste Materials. J. of the Sciences of Food 
and Agriculture 22:164) is discussed:

    "Oddly, the addition of either leguminous leaves alone (peas,
    alfalfa) or non-leguminous leaves alone did not stimulate biogas
    production very much, although there was some result. The addition
    of cane sugar alone, or what they refer to as "sarson oil cake"
    alone, or filter paper (essentially pure cellulose) alone, had no
    effect on the total amount of gas produced. Ashes and charcoal
    both reduced gas production, charcoal rather dramatically.
    (Although some researchers claim that activated charcoal helps
    city sewage digestion and gas production.)"


I agree with you that the source of and method for producing the 
charcoal will very likely have an impact on the result. (In my current 
project-- a 10 cu m food waste digester in a solar greenhouse-- if I 
can find a good source I have been planning to use bamboo charcoal, 
for reasons that I will not mention here since I may well be wrong...)

Of course, several steps in the biogas process are rate-limited, 
particularly (depending on substrate) the first stage, hydrolysis. For 
this and other reasons, /if the mode of action is focused on 
methanogenisis/, I would not expect dramatic improvements in the rate 
of gas production, particularly on the rate of methane production. 
However, whereas as I believe you indicated biofilms will have a lot 
of surface to colonize in most substrates that have any solid 
material, nevertheless it would seem that if the charcoal were in a 
mesh bag and anchored near the inlet to a digester, colonization of 
incoming substrates would take place at an accelerated rate. Where the 
bitty buddies get started faster, then it would stand to reason that 
the whole process would be somewhat accelerated, although I doubt I 
will be seeing a 3x increase.

Some other possible modes of action have already been mentioned, but I 
might just draw a distinction between absorption and adsorption; the 
latter is more of a surface phenomena, and may in some way assist the 
utilization of fatty acids because they would tend to be oriented 
similarly across a surface... I am only speculating, however.



d.
-- 
David William House
"The Complete Biogas Handbook" |www.completebiogas.com|
/Vahid Biogas/, an alternative energy consultancy |www.vahidbiogas.com

|
"Make no search for water.       But find thirst,
And water from the very ground will burst."
(Rumi, a Persian mystic poet, quoted in /Delight of Hearts/, p. 77)

http://bahai.us/
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