[Digestion] Dry fermentation in developing countries

Alexander Eaton alex at sistemabiobolsa.com
Thu Oct 28 09:37:22 PDT 2010

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?


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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Alexander Eaton
Sistema Biobolsa

Mex cel: (55) 11522786
US cel: 970 275 4505

alex at sistemabiobolsa.com
alexanderb.eaton at gmail.com
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