[Digestion] [Gasification] Karve connecting Biochar and Biogas

[Duncan Martin]

It's interesting to see reports of variable effects from additions of
charcoal/ biochar.

To my mind, that supports my hypothesis that it acts primarily as an
ad/absorbent, rather than as a biomass support.

In well-balanced digester, charcoal might reduce the availability of
nitrogen or other key nutrients > process slowdown.

On the other hand, in a digester suffering from an excesss of one nutrient
(eg N) or an adverse concentration of an inhibitor, charcoal might reduce
its concentration > process acceleration.

AD is a very simple process in principle - but it's rarely simple in
practice!

Duncan Martin
Cloughjordan Ecovillage
Ireland



On 8 October 2011 03:49, David <david at 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/
>
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