[Digestion] Identifying organisms in biomethanation

[adkarve]

----- Original Message -----
From: adkarve <adkarve at pn2.vsnl.net.in>
To: Discussion of biomass cooking stoves <stoves at listserv.repp.org>
Sent: Monday, May 14, 2007 11:27 AM
Subject: Re: [Stoves] Dung based Biogas Plants


> I started experimenting with biogas generation only in 2003. But as a
> biologist, I was always interested in this technology. A bit of
information
> that I obtained in 1983 in the course of a presentation that I attended at
> The Institute of Biology II, Freiburg University, Germany, helped me
greatly
> in understanding this process. It was a presentation by two Germany
> researchers. They claimed that practically any organic substance could be
> converted into methane, even benzene or petroleum. The researchers used a
> long, spirally laid plastic tube filled with a dilute emulsion of dung.
They
> introduced, at a time, only one specific organic material as the
substrate,
> and passed it slowly through this tube. It took several weeks for the
system
> to get adapted to the substrate, but after the system had started to
produce
> methane, they found that the bacteria conducting a specific step in the
> conversion, occupied a specific zone within the tube. Thus, if the
substance
> had to go through conversion stages from A to F, the bacteria in the first
> section would convert A to B. then came the zone in which B was converted
to
> C, followed by zones of conversion from C to D, D to E and E to F. The
> methanogenic zone was always the last one. With this system they could
show,
> that if a substance was not directly digestible by the methanogens, the
> concerned substance was degraded, step by step, by several other species
of
> bacteria, that conducted the intermediate stages of conversion, before
> offering it to the methanogens. The main theme of the presentation was
> conversion of mother liquor from a paper factory into methane, but the
> experiments with the long plastic tube not only impressed me, but also
> helped me in understanding the process of biomethanation. It also raised
> several questions in my mind. Since our intestines also represent a
tubular
> system, does the plastic tube model mimic the intestine? Are there zones
in
> our intestine that are occupied by a particular species of bacteria? Is
this
> nature's way of detoxifying material that is not directly digestible by
the
> animal system?
> My experiments later on showed that the methanogens can directly digest
> sugar, certain polysaccharides like starch, mucilages, etc., and also fats
> and proteins. All the above substances yield roughly 250 g methane from a
kg
> of substrate. When one uses cellulose, the methane production is just half
> as much as from sugar or starch, and the reaction time is doubled, because
> the material must first be digested by cellulolytic organisms, before the
> methanogens can take over.
> All the facts mentioned above, and even the plastic tube experiment, may
be
> quite well known to persons who have systematically studied
biomethanation.
> But I thought that the above information might be of interest to
neophytes.
> Yours
> A.D.Karve
>
> ----- Original Message -----
> From: Harmon Seaver <hseaver at gmail.com>
> To: Discussion of biomass cooking stoves <stoves at listserv.repp.org>
> Sent: Monday, May 14, 2007 7:39 AM
> Subject: Re: [Stoves] Dung based Biogas Plants
>
>
> > Simon and Zoe wrote:
> > > Dear All,
> > >
> > > let's not forget that there are very significant advantages to using
> dung based biogas plants:
> > >
> > >  - Feedstock is processed by cattle for free,
> >
> >   And if you don't have cattle?
> >
> > > their digestion systems mulch up the difficult to digest parts of
plant
> cells but still leave some nutrients behind.
> > >  - Families do not need access to a few kilos of raw starchy material
> every day
> >    They could easily gather that from the wild. Cattail roots, for
> > instance, contain 40& starch and a "few kilos" would be overkill.
> >
> > > (most rural Nepalese families certainly cannot afford to throw
potential
> food into biogas digesters).
> >
> >    I think Dr. Karve clearly states food is not used, but that: "It
> > operates on waste starch (spoilt grain, nonedible seed of various
> > species, oilcake of non-edible oilseeds, rhizomes of banana, canna,
> > nutgrass, arums, flour swept from the floor of a flour mill etc.) and
> > produces about 800 litres of gas from just 1 kg starch."
> >
> > > Cattle may graze freely for part of the day, or be fed with gathered
> leaves / grass etc.
> >
> >   If cattle can graze, it is extremely foolish to feed them with
> > "gathered leaves or grass". That entails a lot of needless human work.
> > Plus they will definitely not get as good a diet as when they are
> > allowed to choose their own food. Better for the humans to go gather a
> > little bit of cattail roots or other starchy wild plants to feed the
> > digester.
> >    I think it is quite clear that Dr. Karve's digester method is light
> > years ahead of dung based digestion unless you have a manure waste
> > problem (human or animal) that you need to deal with.
> >
> > > - Two cows are enough to supply a digester sufficient to produce gas
for
> a family.
> > > - Plants are simple to operate & potentially very long lasting, Nepal
> uses the Chinese dome design which has no moving parts (ie. no floating
gas
> container).
> > >  - Domestic toilets are (nowadays) normally also connected, processing
> in the digester neutralises the harmful bacteria often contained in human
> waste and keeps it out of the water supply system.
> > >
> >
> >
> > --
> > Harmon Seaver
> >
> > _______________________________________________
> > Stoves mailing list
> > Stoves at listserv.repp.org
> > http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org
> > http://www.bioenergylists.org
>