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 <[email protected]>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 <[email protected]> > Date: 16 May 2011 09:17 > Subject: Re: Digestion Digest, Vol 7, Issue 13 > > To: [email protected] > > > 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" <[email protected]> >> To: "'For Discussion of Anaerobic Digestion'" >> <[email protected]> >> Subject: Re: [Digestion] Fwd: The biology of biogas production >> Message-ID: <00fb01cc3606$7e81c800$7b855800$@[email protected]> >> 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:[email protected]> mailto:[email protected] >> >> <http://www.adelaide.edu.au/directory/paul.harris> >> http://www.adelaide.edu.au/directory/paul.harris >> >> From: [email protected] >> [mailto:[email protected]] On Behalf Of Anand >> Karve >> Sent: Thursday, 2 June 2011 12:50 PM >> To: [email protected] >> Subject: [Digestion] Fwd: The biology of biogas production >> >> >> ---------- Forwarded message ---------- >> From: Anand Karve <[email protected]> >> Date: 2011/6/2 >> Subject: Re: [Digestion] The biology of biogas production >> To: Gasan Osojnik <[email protected]> >> >> 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 <[email protected]> >> To: [email protected], For Discussion of Anaerobic Digestion >> <[email protected]> >> Subject: Re: [Digestion] Fwd: The biology of biogas production >> Message-ID: <[email protected]> >> 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 <[email protected]> >> To: For Discussion of Anaerobic Digestion >> <[email protected]> >> Subject: Re: [Digestion] Fwd: The biology of biogas production >> Message-ID: <[email protected]> >> 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 >> > > > _______________________________________________ > Digestion mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > > http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org > > 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/ > > > -- -- B.Murali Krishna| Chairman| Village Vision Bio-Power Pvt.Ltd |17-1-380/E/11| Second Floor|ChandraComplex|I.S.Sadan|Saidabad| Hyderabad|500059|AndhraPradesh|India| Ph:+91-40-24333333/24333355/24333555| E-Mail:[email protected]| Web:www.vvi.co.co.in
_______________________________________________ Digestion mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org 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/
