[Stoves] [Digestion] Karve connecting Biochar and Biogas

[Crispin Pemberton-Pigott]

Dear Friends of BioGas

 

I have received a complex reply from David House (Author of the Biogas
Handbook) on  the question of charcoal in the digester and have separated
the relevant parts below for your perusal. It was mixed with a longer
communication so it is paraphrased here and there. The point in presenting
it to this list is that stovers should know not to change feed stocks
willy-nilly and expect the gas unit not to notice. Charcoal might be used in
an inoculation zone only meaning not nearly so much of it is required (i.e.
you don't have to fill up or coat the whole chamber). 

 

Regards

Crispin

 

 

Paraphrased From: David [mailto:david at h4c.org] 
Sent: October-06-11 1:39 PM



The high production rate for the ARTI digester really about the rate of gas
production times the amount of gas production per unit weight from highly
labile, easily digested food wastes. It is topologically equivalent to a
number of previous efforts, such as work done or reported by FAO in the
mid-'80s, and work done as early as 1920 had shown such inputs would have
the effect described. 

 

I think it is quite probable that the proper addition of the right kind of
charcoal to a digester will have a beneficial effect, although I doubt that
in most cases the effect would be as dramatic as described. After all, the
biology is likely to be rate-limited by steps that are unlikely to be
impacted by the addition of charcoal. 

 

I plan to put a mesh bag filled with a certain kind of charcoal near the
inlet of the digester, and perhaps scattered in other places therein, if I
can figure out a proper anchoring system. My primary purpose is to encourage
immediate inoculation of the incoming material, and to insure that there is
a large, robust and stable reservoir of slow-growing methanogens such that
process stability is better assured (i.e. wash-out is far less likely).

However, I would suspect that the proper kind of charcoal-- that is, with
the proper structure, with many open cells, a honeycomb-- would encourage
colonization of a vigorous methanogenic biofilm, and provide greater surface
area for reactions. 

 

Further, it may well be that certain kinds of charcoal tend to selectively
absorb (and/or perhaps adsorb) and present nutritive chemicals for
utilization by the biota, or perhaps functionally neutralize toxic
chemicals. It may even act, in effect, to further buffer the organic acids
in the slurry. In sum, regardless of the mode or modes of action, I would
not be surprised to find it has a beneficial effect-- although again under
the proper circumstances, etc.

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/

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20111007/23780dd5/attachment.html>