[Digestion] Dry fermentation in developing countries

Joshua Bogart joshua.bogart at gmail.com
Thu Oct 28 10:06:48 PDT 2010


 My experience installing poly film digesters taught me to keep it as simple
as possible to limit the abandonment of the systems afterwards. So in this
idea of keeping it simple. What if you evacuated the gas using the exhaust
from a car, many of the how to manuals I read when I was carrying out my
Biogas project recommended this for inflation of digesters made of poly
film. After initial testing I decided not to use it as it adds a step and I
didn't see much advantage when I did and didn't use it. But that way you
would be mixing a low oxygen gas into the digester to make sure that the
Methane was evacuated. I imagine when you stopped getting a flame you would
be safe to allow air to enter. But I might be wrong.

On Thu, Oct 28, 2010 at 10:37 AM, Alexander Eaton
<alex at sistemabiobolsa.com>wrote:

> In a developing world context, it would also make sense to utilize the as
> much of the gas production as possible, meaning that maybe a two-chamber
> system would make the most sense so that you could allow the HRT to be 100+
> days in each chamber.  Then, if there was a flexible portion of each chamber
> that could be compressed while venting you would be able to essentially
> eliminate any risk of an explosive mixture inside the system.  My point it
> that it would make sense to push the gas through to the end-use, then open
> the chamber while it was empty.  Under that scenario I see very little
> risk.  I may also be talking at a small scale, as I am imagining chamber of
> maybe 50 m3 and smaller.  Dry digestion for us would be a huge step, as we
> have a water limitation that keeps us from installing digesters in many
> areas of Mexico and Latin America.
>
> I am returning from the UN Genus waste to energy meeting in Costa Rica,
> where I did have a really interesting discussion about a multi-chambered dry
> digester system for food waste and solid waste collected at a larger level
> and installed at landfills.  In that scenario, I also envision some sort of
> flexible cover that could be vacuum pumped empty before the cover was
> opened.  We were also talking about cells with 2+ year HRTs.
>
> Does anyone have some good info on dry digestion, appropriate substrates,
> HRTs and gas production rates?
>
> A
>
> On Thu, Oct 28, 2010 at 10:22 AM, David <david at h4c.org> wrote:
>
>>
>> Yvonne,
>>
>> On 10/28/2010 1:53 AM, Voegeli, Yvonne wrote:
>>
>> After visiting a Bekon biogas plant in Switzerland, I’m especially
>> concerned regarding the opening of the digester for emptying and refilling.
>> Before opening the door, the digester has to be vented in order to avoid a
>> gas-air-mixture which is explosive. This installation seems to me rather
>> complicated....
>>
>>  ...Is it possible to install a simpler venting system?
>>
>>
>> I would venture a guess that where the inlet air is being forced in by
>> bubbling through water, and the outlet air likewise is allowed to escape by
>> bubbling through water, then the only place in the system where there would
>> be both a potentially explosive gas mixture and the potential of a spark
>> would be at the evacuation point of the exiting gas mixture. Where
>> sufficient air is blown over the water through which the evacuating air is
>> exiting, then the risk of any explosion would, I would think, be very close
>> to zero.
>>
>>
>>
>> d.
>> --
>> 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)
>>
>> http://bahai.us/
>>
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>> Beginner's Guide to Biogas
>> http://www.adelaide.edu.au/biogas/
>> and the Biogas Wiki http://biogas.wikispaces.com/
>>
>>
>>
>
>
> --
> Alexander Eaton
> Sistema Biobolsa
> IRRI-Mexico
>
> Mex cel: (55) 11522786
> US cel: 970 275 4505
>
> alex at sistemabiobolsa.com
> alexanderb.eaton at gmail.com
> sistemabiobolsa.com
> www.irrimexico.org
>
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>
> for more information about digestion, see
> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>


-- 
Joshua D Bogart
Program Coordinator
Trees for the Future
Siguatapaque HN
Barrio Macaruya, Calle, 21 de Agosto
cellular (504) 9696-3700
home/casa 740-1060
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