[Digestion] The biology of biogas production

[Gasan Osojnik]

Dear David,

My engineering book covers most of the written topics (Deublein &
Steinhauser's Biogas form waste and renewable resources (Willey, 2009)),
encluding the biochemisty of the biogas formation from various sources
(points 2. and 4.), but i guess pollution engineering handbook should do. I
will get back to you with the references for the microbiological part.

Excuse me on my quick-fingers terminology, nor "stochiometric" or
"stechiometric" but "stoichiometric" should do fine :)

BR, Gasan


On 23 March 2011 09:18, David Fulford <davidf at kingdombio.com> wrote:

>  Dear Gasan and listers,
>
> This is the sort of information we need on the biogas wiki. Can you provide
> us with some basic references (books, academic articles) that we can use for
> this data, especially on item 2. This is the clearest statement I have read
> on the relative proportions of CH4/CO2 from various substrates.
>
> Do you mean stochiometric, or is stechiometric another term that we need to
> learn?
>
> Thanks
>
> David F
>
>
> On 23/03/2011 07:49, Gasan Osojnik wrote:
>
> Dear dr. Karve
>
> I do not wish to engage nor in a lengthy philosophical or physiological
> debate, but I do have one or two points to make:
>
> 1. Methanogenic archaea do not degrade sugar or even complex substances,
> they use either acetate or hydrogen + carbon dioxide to survive. They are
> old an primitive organisms, that originate back to the beginning of life,
> even before glucose was formed by other organisms, therefore they can feast
> on very basic energy sources.  There are not any other "methanogens" in
> other branches of the evolution tree.
> 2. The stechiometric ratio of methane/carbon dioxide fromation from
> carbohydrates is CH4/CO2 = 50/50, from fats = 62.5/37.5 and from proteins
> 71/29 (due to absorptive properties of the sediment), so the number
> mentioned is presumably based on anaerobic microbial protein degradation?
> 3. The chain of microorganisms is not only highly likely, but is confirmed
> by the means of certified analytical techniques, such as the techniques of
> molecular biology and can be even seen under the  electron microscope. The
> sole biochemistry and the termoenergetics of the methane formation process
> from polymers reveal, that it is impossible for the process to start and
> finish in only one type of unicellular procaryotic microorganisms (or any
> other). We have pictures of microorganisms of species that are literary
> "glued one another" for better substrate / intermediate exchange, and this
> is no exception but a necessity for their survival. Currently it is believed
> that around 800 species are involved in the biogas formation community (not
> all at the same time) but this number is increasing rapidly (e.g. 2008 this
> number was around 400). Personally I believe this number to be much greater,
> as methanogenic microbiota is found on very diverse parts of the planet and
> is a common way of surviving in areas with no / low oxygen concentrations.
> 4. The issue of  CO2 which has ben adressed needs some basic insight in the
> process. The dissolved co2 that is produced intermediately in the proceses
> of acetogenesis (some also in the  hydrolysis ans acetogenesis) is, as said,
> a substrate for the production of methane, and is taken up very rapidly  by
> the archaea. Therefore, you should not look at the intermediate CO2 as a
> product but as a reactant. As most of the biogas (at least up to 70%) is
> formed via acetate decarboxylation to methane and CO2. The partial pressures
> of surplus CO2 equilibrate in the headspace of the reactor and the liquid,
> so the CO2 that you get in biogas is actualy mostly the product of
> acetoclastic methanogenesis.
>
> BR, Gasan
>
>
> Dear Mr. Afilal,
> if you used any substance that is digested by humans,(sugar, starch,
> digestible protein or fat), it gets completely converted into biogas by
> the methanogens. 1 kg of any of these substances would yield about 1 kg
> biogas, containing the theoretically calculated proportion of roughly 25 to
> 30% methane and 70 to 75% carbon dioxide. The presence of a chain of
> micro-organisms, with each one producing a product that serves as food for
> the next one in the chain is not believable. If it were really so, one
> would
> get a much higher concentration of carbon dioxide in the resultant biogas,
> because the intermediate organisms produce only carbon dioxide and not
> methane.
> Yours
> A.D.Karve
>
>
>
> On 22 March 2011 20:00, <digestion-request at lists.bioenergylists.org>wrote:
>
>> Re: The biology of biogas production
>
>
>
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>
>
> --
>
> ********************************************************************
> Dr David Fulford CEnv MEI, 15, Brandon Ave, Woodley, Reading RG5 4PU
> d.j.fulford at btinternet.com, Tel: +44(0)118 326 9779 Mob: +44(0)7746 806401
>
> Kingdom Bioenergy Ltd, www.kingdombio.com, davidf at kindombio.com
>
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