Dear List, I did not say that the biogas production was accelerated by filling charcoal in the digester. All I claimed was that a 1000 litre food waste digester which normally accepted daily only 1 kg (dry weight) of food waste, could accept daily 3 kg and also produced 3 times as much biogas, when a bagful of charcoal was kept in the digester. We got similar results also with pieces of bamboo instead of charcoal. I had also mentioned my hunch that this was a case of providing a larger surface area for the micro-organisms to settle on. This is a fairly routine practice in many fermentation reactions. Yours A.D.Karve On Sat, Oct 8, 2011 at 10:49 AM, David <da...@h4c.org> wrote: > > > 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/ > _______________________________________________ > Digestion mailing list > > to Send a Message to the list, use the email address > digest...@bioenergylists.org > > 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/ > > >
-- *** Dr. A.D. Karve Trustee & Founder President, Appropriate Rural Technology Institute (ARTI) _______________________________________________ Digestion mailing list to Send a Message to the list, use the email address digest...@bioenergylists.org 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/
