[Digestion] Dry fermentation in developing countries

[Voegeli, Yvonne]

Dear all,

I like to start a new discussion on a different topic, namely the dry-fermentation process (discontinuous) similar to the digesters developed by the companies Bekon or Bioferm in Germany. The organic waste is filled batch-wise into simple garage-like digesters for about 30-40 days.

Experts report that this process has a high potential for application in developing countries as it has the simplest design and the solid waste digesters are the least expensive ones. Also, substrates that lead to operating problems during wet fermentation due to their structure or the proportion of impurities they contain can still be processed using dry fermentation methods. However, up to date, there is no experience with this technology in developing countries. Therefore, our idea is to develop a dry-fermentation biogas plant adapted to the situation in developing countries using locally available material.

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 anybody of you familiar with discontinuous dry-fermentation systems and has an idea how the security can be assured in a developing country context? Is it possible to install a simpler venting system?
- Likewise, when removing the drum from a floating-drum digester for emptying, how is ensured that at no time an explosive gas-air-mixture occurs?

Thanks for your ideas,
Yvonne
°°°
Yvonne Vögeli
Eawag / Sandec
Überlandstrasse 133
P.O. Box 611
8600 Dübendorf
Switzerland
Phone: +41 (0)44 823 54 20
Fax: +41 (0)44 823 53 99
yvonne.voegeli at eawag.ch
http://www.sandec.ch

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