Building a Poly Bio Digester
The following may be of use to those considering building a poly digester.
Remember that you are dealing with bacteria and (hopefully) flamable/explosive gas, so reasonable SAFETY precautions MUST be used.
Seek professional advice for any commercial project!
Power Point presentation by Francisco Aguilar
You may be interested in a "Do It Yourself" Manual.
If you do build a digester the Syringe Protocol provides a cheap method of finding the biogas composition. More than 50% Methane will burn with a stable flame.
Paper by Francisco Aguilar
Paper by Lylian Rodriguez and T.R. Preston, who also have a CDROM version of the Manual (e-mail Lylian Rodriguez and ask for it)
The above were also used in an E-Conference, with many interesting topics in the Discussion
Drawings of "graves", simple burner and photos of small digester by Paul Harris. The material is "layflat tubing" that I get from a poly bag manufacturer. Any company making plastic sheet should be able to supply some tube (sheet before it is split!)
Photos of Construction by Takasi Yanagida
More photos by Paul Harris
Student Report by Luke Jenangi
You may like to look at an Excel model (of a continuous flow stirred tank digester, but the interactions should be similar).
There is also a book - "Toward a better use of our natural resources", published by EARTH university, Costa Rica, 1999,
which has an article "The Biodigester" by Botero, R.; Aguilar, F. and Preston, T.