The dome shape is inherently sturdy, compact and material-sparing. The digester is easy to build,
and the techniques can be learned by local craftsmen in a short time (cf. fig. 5.21).
Water-jacket plant (cf. fig. 5.7)
Water-jacket biogas plants are characterized by a long useful life and a more aesthetic appearance
(no dirty gasholder). Due to their superior hygiene, they are recommended for use in the
fermentation of night soil and for cases involving pronounced scumming, e.g. due to rapid
evaporation, since the gasholder cannot get stuck in the scum. The extra cost of the masonry water
jacket is relatively modest.
Cylindrical plant for quarrystone masonry and concrete (cf. fig. 5.8)
It is anything but easy to make a dome-shaped digester out of quarrystone masonry; it is much
easier to build a concrete cylinder. In such cases, the classical (Indian) version with a cylindrical
digester is quite practical Note: Quarrystone masonry consumes a lot of mortar.
Fig. 5.6: Floating-drum plant with internal
guide frame. 1 Mixing pit, 11 Fill pipe,
2 Digester, 3 Gasholder, 31 Guide frame,
4 Slurry store, 41 Discharge pipe, 5 Gas pipe,
51 Water trap (Source: Sasse 1984)
Fig. 5.7: Water-jacket plant with external
guide frame. 1 Mixing pit, 11 Fill pipe,
2 Digester, 3 Gasholder, 31 Guide frame,
4 Slurry store, 5 Gas pipe
(Source: Sasse 1984)
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