[Digestion] young scientist project

Mon Aug 6 08:32:27 EDT 2007

This is all useful information for experimenters like Duncan and  
myself, thank you.

May I just check Dr Karve, don't you normally seed the starch-based  
digester with animal dung??

thanks

kind regards

Marcel

On 6 Aug 2007, at 04:24, adkarve 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 <duncanjmartin at eircom.net>
> To: adkarve <adkarve at pn2.vsnl.net.in>
> 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" <adkarve at pn2.vsnl.net.in>
>> To: <digestion at listserv.repp.org>
>> 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 <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
>>>>> _______________________________________________
>>>>> Digestion mailing list
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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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>>>> http://info.bioenergylists.org
>>>
>>>
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>>
>
>
>
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