[Digestion] Fwd: The biology of biogas production

Fri Jul 1 22:14:25 CDT 2011

Good day Gasan,

Fixation of CO2.that I was discussing is at fermentation stage.

Krishna

On Thu, Jun 30, 2011 at 11:14 AM, Gasan Osojnik <gasan.osojnik at gmail.com>wrote:

> I have shared my thoughts on the matter earlyer with dr. Karve, and as this
> debate has gotten some mettel on this list, I am posting my reply here,
> likewise.
>
> The biochemistry of biogas production dictates that CO2 and CH4 must be
> produced simultaneously to achieve stable operation. The product CO2/CH4
> ratio is governed by the type of substrates used. There are two main
> pathways (also some others that are currently regarded as exceptions & less
> important) of biochemical pathways, that result in biogas:
>
> - acetoclastic pathway (acetic acid is decarboylized to methane and carbon
> dioxide)
> - hydrogenotrophic pathway (hydrogen and carbon dioxide are utilized to
> form methane alone)
>
> As both these processes are are mutually dependable on the other one, CH4
> and CO2 must be formed together, or none at all. An e disturbance in theeither one of these processes results in
> the condition which I'm sure we are all familiar with, t.i. theacidification of
> the reaction. The amount of H+ in the broth becomes easily toxic to
> acetoclastic methanogens, therefore in a stable process, all the H+ must
> react with the dissolved carbonate, and the carbonate that remains is
> therefore the source of final CO2 in the biogas.
>
> Further on, regarding the CO2 fixation from the gas phase above the
> fermentation broth (e.g. in digesters equipped with  floating drum,
> inflatable cover and similar); the methane ration in the "headspace" does
> not affect the level of methane production, as the amount of the methane
> that is made is governed by the biochemical properties of the substrate.
> Also, methane is poorly soluble in water , so there is no physiochemical
> mechanisma that would neable the microorganisms to "know" what the methane
> content in the produced biogas is.
>
> Interesting mechanism described by Khrishna, are you refering to the CO2
> fixation from the gas phase (biogas) or from the liquid phase (fermentation
> broth itself)?
>
> I remember some systems were proposed, where the CO2 formed due to methane
> combustion in the cogeneration plant would be purged through the
> fermnetation broth to achieve higher methane yields, but I have no knowledge
> if any commercial applications of this exist.
>
> Also, I think, there is the general problem of carbon dioxide that must be
> addressed, as we must start to view the produced CO2 as a product and not
> as an impurity. A vast amount of biochemical energy is used to produce
> carbon dioxide in the biological process, so by utilizing the produced CO2
> rather than discarding it, the energy efficiency of such processes could be
> considerably increased. E.g. the  biogas plants can be could be coupled to
> greenhouses to enhance the productivity of plants. Similarly, there are
> attempts being made, to flue gases from biogas co-generation units to feed
> the algae plantations. Further on, a wast scientific community is quite
> successful in researching new ways to catalytically transform ch4 and co2 to
> synthesis gas or similar intermediates, that can be further transformed to
> various high-value chemicals.
>
> BR from SI, Gasan
>
> ------------------------------
> From: Gasan Osojnik <gasan.osojnik at gmail.com>
> Date: 16 May 2011 09:17
> Subject: Re: Digestion Digest, Vol 7, Issue 13
>
> To: digestion at lists.bioenergylists.org
>
>
> Dear David and Melvin,
>
> I apologize for not responding sooner, a lot of things were prioritized.
> Here is the full sources list for the basic anaerobic degradation described
> on 23 Mar 2011 in the topic "The biology of Biogas Production".
>
> (i) As already mentioned, basic biology for engineering purposes (encluding
> the biochemisty of the biogas formation from various sources) is explained
> in:*
> Deublein & Steinhauser's Biogas form waste and renewable resources (Willey,
> 2009))* and many other pollution engineering handbooks.
>
> (ii) The microbial syntrophism explained (interspecies hydrogen transfer),
> essential for biogas production, is explained in e.g.:
> *Schink, B (1997) Energetics of syntrophic cooperation in methanogenic
> degradation. Microbiology and Molecular Biology Reviews, 61 (2), 262-280*,
> (an example was explained already in 1967 by *Bryant et al.,
> Methanobacillus omelianskii, a symbiotic association of two species of
> bacteria.
> Arch. Microbiol. 59:20.*)
>
> (iii) Regarding the biodiversity in the reactor, the number 800 species was
> given recently at a lecture from prof. Romana Marinsek-Logar from UL. In a
> recent publication, *Jaenicke et al (2011), Comparative and Joint Analysis
> of Two Metagenomic Datasets from a Biogas Fermenter Obtained by
> 454-Pyrosequencing,* the taxonomic profile of the biogas producing
> community is updated with several new genera (s.a. *Streptococus* and
> genera in the* Firmicutes* phylum), altogether 40 genera was identified.
> Furthermore, I'm am anxios to see the outcome of the biogas-producing
> microbial community sequencing (Martin Wu, UC Davis & DOE JGI), a project
> which is bound to produce interesting results.
>
> (iv) General facts about *Archaea* etc. can be found in *Brock's Biology of
> Microorganisms** *and in *Bergey's Manual* .
>
> (a.d.) Also, i have come across an interesting educational cartoon
> describing the biological process of biogas formation . It is informative
> and has one or two slips (e.g. in the animation water is added after the
> hydrolysis, where in fact it has to be present before the process for the
> decay of complex molecules), but still very nice to see.
>
> http://www.youtube.com/watch?v=bUBAndojs50&feature=player_embedded
>
> BR, Gasan Osojnik
>
>
> ------------------------------
>>
>> Message: 3
>> Date: Wed, 29 Jun 2011 12:14:39 +0930
>> From: "Paul Harris" <paul.harris at adelaide.edu.au>
>> To: "'For Discussion of Anaerobic Digestion'"
>>        <digestion at lists.bioenergylists.org>
>> Subject: Re: [Digestion] Fwd:  The biology of biogas production
>> Message-ID: <00fb01cc3606$7e81c800$7b855800$@harris at adelaide.edu.au>
>> Content-Type: text/plain; charset="iso-8859-2"
>>
>>
>> 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
>>
>> Mr. Paul Harris, Room 202 Charles Hawker Building, Faculty of Sciences,
>> The
>> University of Adelaide, Waite Campus, PMB 1, Glen Osmond SA 5064 Ph    :
>> +61
>> 8 8303 7880      Fax   : +61 8 8303 4386
>> <mailto:paul.harris at adelaide.edu.au> mailto:paul.harris at adelaide.edu.au
>>
>> <http://www.adelaide.edu.au/directory/paul.harris>
>> http://www.adelaide.edu.au/directory/paul.harris
>>
>> 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
>>
>> ------------------------------
>>
>> Message: 9
>> Date: Wed, 29 Jun 2011 22:23:27 +0800
>>
>> From: Anand Karve <adkarve at gmail.com>
>> To: paul.harris at adelaide.edu.au, For Discussion of Anaerobic Digestion
>>        <digestion at lists.bioenergylists.org>
>> Subject: Re: [Digestion] Fwd: The biology of biogas production
>> Message-ID: <BANLkTi=iCPU9n=ULeu9W-5JM6+MNCXWAMQ at mail.gmail.com>
>> Content-Type: text/plain; charset="iso-8859-2"
>>
>> 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
>>
>> ------------------------------
>>
>> Message: 11
>> Date: Wed, 29 Jun 2011 21:55:08 +0530
>> From: Murali Krishna <bmkrishna6 at gmail.com>
>> To: For Discussion of Anaerobic Digestion
>>        <digestion at lists.bioenergylists.org>
>> Subject: Re: [Digestion] Fwd: The biology of biogas production
>> Message-ID: <BANLkTimK=jpAkgRjbfxa+HJbdpnncQV2RA at mail.gmail.com>
>> Content-Type: text/plain; charset="iso-8859-2"
>>
>>
>> Good day Paul,
>>
>> CO2 is isolated and streamed into a separate chamber.  Carbonic Anhydrase
>> enzymes are used to isolate CO2 from the digester. Carbonic anhydrase,
>> rapidly converts carbon dioxide to bicarbonate. Thus CO2 is efficiently
>> removed  from the solution in the digester. The product of this reaction,
>> bicarbonate, can then be reacted with sodium to form NaHCO2, baking soda.
>> By this process CO2 emission into atomosphere is reduced substantially and
>> there is more space in the digester. There is a patent on this.
>>
>> The isolated CO2 after modifications is sent back into the digester and
>> Methane is generated.  (This second part I need to yet confirm). I shall
>> come back to you soon on this.
>>
>> Krishna
>>
>
>
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> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>

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