to take place. Moreover, the cracking of the dome is also avoided by the temperature
and moisture change (Singh et al. 1987).
Operating Procedure
1. Feed the organic wastes like manure, dung, human excreta, etc.
2. The methanogenic bacteria decompose the raw material.
3. Biogas and the digestate are produced.
4. Gas is stored in the dome, and the slurry is displaced into the compensation tank.
5. When the gas is utilized, the pressure decreases and the proportional quantity of
the slurry pushed back into the digester. So the pressure of gas varies depending
on the gas production and the usage (Kudaravelli 2013; Stalin 2007).
Advantages of Fixed-Dome Digester
1. Inexpensive.
2. Longer lifespan if well constructed (20 years or more).
3. Less susceptible to corrosions.
4. Sub-surface assembly saves space and reduces variation in temperature (Werner
et al. 1989).
5. Creates local employment.
Disadvantages of Fixed-Dome Digester
1. To construct such gas-tight structure and bedrock, it requires capital and expertise/technical skills.
Fig. 3.10 Schematics and workflow of fixed- dome digester. (Modified from Florentino 2003;
Samer 2012; Sasse 1988; Vögeli et al. 2014)
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