Floating Dome

Submitted by Thomas H. Culha... on
Last changed on 21 Dec, 2015 - 13:25

A floating drum digester consists of a fixed base and flexible top. It was established in India after early British sanitation efforts. Its basic principle is those of gravity and the different specific weights of molecules, in this case Methane and water.

Build Instructions


Two cylindrical water tanks, one fitting inside the other.


  1. Cut the top off of the larger diameter tank. 
  2. Cut holes out of the top of the smaller diameter tank.
  3. Turn the smaller diameter tank upside down. 
  4. Put a 1/2 inch uniseal in the bottom of the smaller diameter tank (which is now the top of the gas holder).
  5. Put a hole at the bottom of the larger tank and insert a feeding pipe to the middle.
  6. Put a hole about 20 cm down from the top of the larger diameter tank and put a pipe with three elbows in it so that the effluent pipe comes up just near the top of the tank.


Our original tutorial showed the use of a tray inside the digester to give microbes more places to live in the warm area of the tank as shown in the video below:

We have since modified that to the insertion of hanging microbial motels. And we've combined it with the IBC digester, using the ARTI for gas production and storage in the summer and gas storage in the winter (with the IBC producing all year round).

 Over the past 4 years we have decided to cut the top off of the smaller tank and invert it and tie it inside to make an microbe "elevator".