[Digestion] [work] Re: Digestion Digest, Vol 2, Issue 40
david at h4c.org
Mon Oct 25 18:55:46 PDT 2010
On 10/25/2010 1:28 PM, Markus Schlattmann wrote:
> I still don't believe in those 540 m³ from 1000 kg dung....
A sensible analysis. Maybe the key to the conundrum is the statement:
> ...the biogas plant in Wardha... accepts 1000 kg cattle dung as a
> one-time load and produces daily 3 cubic meter biogas continuously
> over a period of 180 days...
It is well known that batch digestion does not produce the same amount
of biogas every day. Obviously it takes some time for the ecology of
the digester to get established (during which time, of course, gas
production is low), and it is surely something approaching a law of
biology that the more digestible components of the substrate will be
used up first, and then some of the more recalcitrant materials will--
eventually-- be digested. The succession of these stages offers a
well-known curve, which is either bell-shaped, if it plots daily
production, or a long S (ogee) curve if we are plotting cumulative
In sum, I have no doubt that biogas is produced, and that for a period
of time production is good. Thus I would accept that the reported
plants produce well for a time, but not that they produce the same
amount every day, continuously for six months. But surely the
statement as quoted has to do with genuine enthusiasm, and should not
be taken as a rigorous mathematical description.
While my search turned up a number of references to the organization
in Wardha in connection with biogas, none provided any reference to
these batch digesters, unless they are very large clay pots, as one
reference mentions. It would be salutary to have some literature on
the subject, if any has been produced.
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)
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