schemes and images on googleimage, showing the large panel of structural options to build a biogas digester, and also the common elemenst of each technical plan
The first result is inn English, it is the guidebook (12 pages) on "Preparing this training material all the important information have been collected from the booklets & research materials".
Source : Biogas Training Center (BRC) Chendu, Sichuan, Chaina.
The author of this HowTo biogas digester might be a good resource person :
http://www.greenoptimistic.com/about-us/
"To construct a good biogas plant, you should not only respect the dimensions as indicated on the drawing but also follow the correct construction method. Hereunder, in a step-by-step fashion, the right construction method of the 2047 design GGC model biogas plant is given."