Fixed-dome digester, L.Sasse (GATE)

Fixed-dome - floating-drum small scale digesters

Agricultural small scale anaerobic digesters - fixed-dome or floating-drum - can help to cover distributed energy demands. Further more anaerobic digestion reduces pathogens and delivers a marketable furtilizer.


There are two main types of simple small scale anaerobic digesters


    • fixed-dome digesters
    • floating-drum digesters


The fixed-dome digester made out of bricks and mortar forms a closed spherical fermantation tank. The overall volume of the digester should not exceed 20m3 due to stability and pressure.

Gas is stored in the upper part of the digester, whereas heavier parts sink to the bottom and the inside gas pressure forces excess sludge to empty into a storage tank.

The fermenter of floating drum digesters is constructed similar to the fixed dome digesters. However, gas storage is handled through a movable steel drum collecting the gas. A water jacket is used as a seal to outside and guides the drum moving up and down.

Small scale agricultural biogas plants, L.Sasse (GATE)