Despite the high salinity, biological processes could be used in salt caverns for methanation if suitable conditions are created. With suitable backfill materials, growth areas for the formation of biofilms could be created and the availability of sulfate could be reduced. These backfill materials can also be used in the course of cavern containment to reduce convergence.
Large scale experiments enable the simulation of cavern filling with suitable porous materials and the testing of growth material to promote biofilm formation. The aim is to develop an underground methanation reactor that also minimizes the convergence of the cavern. Therefore, it has to be tested if methanogenic archaea can survive under the given conditions.
We use an autoclave system with a volume of ca. 35 liters. Pressures of up to 100 bar and temperatures of up to 100 °C are possible. The autoclave consists of two chambers and a 2.5 m long casing in between. For safety reasons, the gas will contain 95 % N2, 4 % H2 and 1 % CO2. The bottom of the autoclave will be filled with brine and salt. As filling materials, expanded clay and construction waste are foreseen.