[Digestion] Fwd: The biology of biogas production

[Anand Karve]

Dear Paul,
The text book opinion is that methanogens are helped by a large number of
other bacteria in the process of methanogenesis. Some time ago I had posed a
question to Gasan that if there are so many different organisms involved in
this process, why we did not get a lot more carbon dioxide in our biogas
than the 40% that everybody reports.  He wrote that the organisms that
associated themselves with the methanogens used the carbon dioxide as the
source of carbon. Gasan may elaborate this point.
Yours
A.D.Karve


2011/6/29 Paul Harris <paul.harris at adelaide.edu.au>

>  G'day A.D. Karve et al,****
>
> ** **
>
> This post from a while back prompted an interesting thought - if you are
> right we may be able to acclimate a digester to using just CO2 as the carbon
> source, so we could convert CO2 back to methane and solve both CO2 emissions
> and "peak oil".****
>
> ** **
>
> The quality ratio of CH4 to CO2 does vary a bit, sometimes being less than
> 50% methane and sometimes claims of over 90% methane, but David Fulford has
> shown that sugar and starch give 50% methane so any improvement is due to
> some methanogens using CO2 produced earlier in the sequence and H+ from
> water and acids to make CH4 and H2O.****
>
> ** **
>
> Happy digesting,****
>
> HOOROO****
>
> ** **
>
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> *From:* digestion-bounces at lists.bioenergylists.org [mailto:
> digestion-bounces at lists.bioenergylists.org] *On Behalf Of *Anand Karve
> *Sent:* Thursday, 2 June 2011 12:50 PM
> *To:* digestion at lists.bioenergylists.org
> *Subject:* [Digestion] Fwd: The biology of biogas production****
>
> ** **
>
> ** **
>
> ---------- Forwarded message ----------
> From: *Anand Karve* <adkarve at gmail.com>
> Date: 2011/6/2
> Subject: Re: [Digestion] The biology of biogas production
> To: Gasan Osojnik <gasan.osojnik at gmail.com>
>
> ****
>
> Dear List,****
>
>  Irrespective of the substrate, design of the system or the temperature of
> the reaction, the proportion of methane to carbon dioxide in the
> biogas seems to be constant all over the world. Is there an
> equilibrium between these two gases that keeps this proportion constant?
> Because in that case, one might introduce carbon dioxide from outside into
> the biogas plant and see if the organisms in the digester produce more
> methane to reach the euilibrium constant. I shall be grateful to get your
> reaction on this. ****
>
> Yours****
>
> A.D.Karve  ****
>
> 2011/3/22 Gasan Osojnik <gasan.osojnik at gmail.com>****
>
> Hi Mohamed,
>
> The general (though I am sure there will be other interpretations)
> mechanism of biogas formation is 4-step and involves:
> 1. Hydrolysis (degradation of polymers)
> 2. Acidogenesis (the formation of volatile fatty acids - low molecular
> carboxylic acids)
> 3. Acetogenesis (the formation of acetate, CO2 and H2)
> 4. Methanogenesis (from acetete -> CO2 and CH4 is formed, from CO2 and H2
> -> CH4 is formed, methanogenesis from acetate and CO2+H2 has to run
> simultaneously for the proces to be stable)
>
> The last step is the reason why there will be always some CO2 in biogas.
> Each of this steps is carried out by different groups of microorganisms.
>
> So the initial biochemical sources of biogas are carbohydrates, proteins,
> fats etc. In the long run, any substance that can be converted
> intermediately either to dissolved CO2 and H2 or to acetate is appropriate
> for biogas production.
>
> BR from Slovenia, Gasan****
>
>  ****
>
> *Ilja Gasan OSOJNIK ČRNIVEC, *L05 - Laboratory for Environmental Sciences
> and Engineering ****
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>


-- 
***
Dr. A.D. Karve
President, Appropriate Rural Technology Institute (ARTI)

*Please change my email address in your records to: adkarve at gmail.com *
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