[Digestion] young scientist project

Thu Aug 9 21:22:43 EDT 2007

Dear Dr Karve,

I have always wondered about water in the digester. The water that submerges feedstock (where methanogenic bacteria live and thrive.) I notice that water quantity is reduced (or lessened) when biogas is produced. 

Is any of the hydrogen (H) and oxygen (O2) in the water converted when methane (CH4) and carbon dioxide (CO2) is produced? If so, how much water is converted? Or, what percentage of the water in the mixture (feedstock & water) is converted. 

Gerry Baron

adkarve <adkarve at pn2.vsnl.net.in> wrote:  Dear Duncan,
Our biogas plant consists of a floating dome type of gas collector. Its
lower end is always immersed in the water in the digester. Therefore, you
have only to add weights on the floating dome to apply pressure on the gas
collected in the dome. I forget now how much weight the students had put on
the dome. Secondly, we use only starchy material (food waste) as feedstock
and no dung at all. Starch is completely digested by the methanogenic
bacteria. C6H12O6=3CO2+3CH4. About 1 kg starch would give you 0.8 cubic
meter of biogas. We call our system compact biogas system. We have already
installed 2500 such plants in India.
Yours
A.D.Karve
----- Original Message -----
From: Duncan Martin 
To: adkarve 
Sent: Sunday, August 05, 2007 1:11 PM
Subject: Re: [Digestion] young scientist project

> Dr Karve
>
> That's a most useful tip in #2 below - many thanks. But I wonder how much
> pressure you needed?
>
> As for #1, that would have been my next suggestion! You are a step ahead
of
> me....
>
> Best regards
>
> Duncan
>
> ================================
> CONTACT DETAILS
> Duncan J Martin, PhD, CEng, CSci, MIEI, MCIWM, MIChemE
> 24 Townsfield, Cloughjordan, N Tipperary, Ireland
> Home: +353 505 42087 
> Mobile: +353 86 8377 906 
> Email: duncanjmartin at eircom.net
> ================================
>
>
>
> ----- Original Message -----
> From: "adkarve" 
> To: 
> Sent: Sunday, August 05, 2007 5:26 AM
> Subject: Re: [Digestion] young scientist project
>
>
> > Dear stephen,
> > 1. you start getting biogas without any time lag if you fill your
digester
> > with slurry from an existing biogas plant.
> > 2. CO2 dissolves in water and slowly diffuses out into the atmosphere.
> > Therefore, collecting biogas in a water filled cylinder held immersed in
a
> > water trough may give you wrong results, but it is also a great method
for
> > getting rid of carbon dioxide from biogas. We conducted this as a
> > students'
> > project and by applying pressure to the biogas in the cylinder, we got
95%
> > pure methane after a week.
> > Yours
> > A.D.Karve
> >
> > ----- Original Message -----
> > From: Duncan Martin 
> > To: stephen cullinan ;
> > 
> > Sent: Saturday, August 04, 2007 2:05 PM
> > Subject: Re: [Digestion] young scientist project
> >
> >
> >> Stephen
> >>
> >> Many methods have been tried but I know of nothing SIMPLE and CHEAP
that
> >> works really well.
> >>
> >> A lot depends on what you want to store biogas for. Usually, at this
> > scale,
> >> it's to measure it.
> >>
> >> First, check that your digester and collection system are 100%
gas-tight,
> > by
> >> a static pressure test.
> >>
> >> I'd avoid the standard lab method of collection in a vessel inverted
over
> >> water (or whatever*). It's likely to lose its seal due to evaporation
> >> over
> >> months of observation, unless you are unusually vigilant about topping
it
> >> up - and never take any holidays. Also the water will become foul
unless
> >> changed from time to time.
> >>
> >> (*Acidified brine is better - but more awkward to work with. Bear in
mind
> >> that even sparingly soluble gases can dissolve and gradually escape
when
> >> stored over water for many weeks.)
> >>
> >> Bear in mind too that a digester can suck gas back at times**, so you
> >> need
> >> to make sure that it has "access" to gas to suck back - or it will pull
> >> in
> >> water (or air).
> >>
> >> (**Various reasons but you can have long periods especially at first,
> >> with
> >> essentially zero biogas production - I assume you plan a batch process.
> >> There might be a few days of rapid CO2 production but then nothing for
> > many
> >> weeks - which isn't great for a Young Scientist project! One 10L
digester
> > of
> >> mine only began to produce biogas after a TWO YEAR lag - but then
> >> accelerated to almost 10L/day. During such a long lag period, suck-back
> > can
> >> be caused by all sorts of things, including small changes in temp or
atm
> >> pressure.)
> >>
> >> One method I found worked quite well was to use the kind of foil
balloons
> >> sold in party shops etc. You can often get old stock quite cheaply (eg
> >> Valentine's Day ones in March!). Liberally grease the outside of a
small
> >> piece of rigid plastic or metal tubing and push it up the nozzle and
into
> >> the balloon. This opens the flap valve in the neck and holds it open,
so
> >> that gas can flow in - and (when you want it) out again, by
disconnecting
> >> the tube from the digester briefly.
> >>
> >> This collects gas at zero back-pressure - until the balloon is almost
> > full -
> >> and you should empty it as soon as it gets to that stage. You could
meter
> >> the gas as it flows out if you want accuracy - but "balloonfuls" might
be
> > a
> >> good enough measure.
> >>
> >> NB As I hinted above, time-scale might be a problem for a Young
Scientist
> >> project, unless you plan to become an Old Scientist in the process!!
What
> > do
> >> you plan to digest and what to seed it with?
> >>
> >> Good luck!
> >>
> >> Best regards
> >>
> >> Duncan
> >>
> >> ================================
> >> CONTACT DETAILS
> >> Duncan J Martin, PhD, CEng, CSci, MIEI, MCIWM, MIChemE
> >> 24 Townsfield, Cloughjordan, N Tipperary, Ireland
> >> Home: +353 505 42087 
> >> Mobile: +353 86 8377 906 
> >> Email: duncanjmartin at eircom.net
> >> ================================
> >> ----- Original Message -----
> >> From: "stephen cullinan" 
> >> To: 
> >> Sent: Friday, August 03, 2007 1:28 PM
> >> Subject: [Digestion] young scientist project
> >>
> >>
> >> >I have developed a mini anaerobic digester. It consists of a plastic
can
> >> > about 30cm by 30cm by 90cm.I have cut a hole in the lid of the can.
In
> >> > this
> >> > lid I placed a mini agitator which contained a pipe leading from the
> >> > top
> >> > of
> >> > the inside of the plastic can to the outside transporting any gas
> >> > produced.Iplaced three of these in a plastic
> >> > box.I placed a small immersion heater into the box and filled the box
> > with
> >> > water. However this is where I am stuck. I need some help in thinking
> >> > up
> >> > of
> >> > a way of trapping the gas
> >> > _______________________________________________
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> >> > http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
> >> > Beginner's Guide to Biogas
> >> > http://www.adelaide.edu.au/biogas/
> >> > http://info.bioenergylists.org
> >> >
> >> >
> >> >
> >> > --
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> > 02/08/2007
> >> > 14:22
> >> >
> >> >
> >>
> >>
> >> _______________________________________________
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> >> Beginner's Guide to Biogas
> >> http://www.adelaide.edu.au/biogas/
> >> http://info.bioenergylists.org
> >
> >
> > _______________________________________________
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> > http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
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> > http://info.bioenergylists.org
> >
> >
> >
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02/08/2007
> > 14:22
> >
>

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