[Digestion] young scientist project

[adkarve]

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 <duncanjmartin at eircom.net>
To: stephen cullinan <stephencullinan at gmail.com>;
<digestion at listserv.repp.org>
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" <stephencullinan at gmail.com>
> To: <digestion at listserv.repp.org>
> 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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> > Beginner's Guide to Biogas
> > http://www.adelaide.edu.au/biogas/
> > http://info.bioenergylists.org
> >
> >
> >
> > --
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> > 14:22
> >
> >
>
>
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> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> http://info.bioenergylists.org