Recently, promising biologically mediated upgrading systems have been suggested, in which H2 and CO2 are biologically converted to CH4 by the action of autochthonous hydrogenotrophic methanogens without any additional energy input. The concept is independent from the utilization of defined microbial cultures (pure cultures) which require a relatively pure source of CO2. Thus, cheap biogas (~60% CH4, ~40% CO2) is used for biological upgrading. In addition, the concept of adding H2 directly to anaerobic digesters has been validated with CH4 purities as high as 95%. For ex-situ biogas upgrading, a crucial technical challenge that should be addressed is the poor liquid mass transfer and the efficiency of the diffusion devices. As an alternative, traditional fixed-bed reactors have been explored to immobilize microbial communities, but several limitations using fixed- bed were found. For example, bubble formation, low solubility of H2 and limitation in mass transfer and the metabolic rate caused by lack of surface. In this project, we develop innovative biotechnological solutions to upgrade biogas to pure biomethane.
To design, operate and optimize bio-trickling filter reactors for ex-situ biological biogas upgrading using mixed hydrogenotrophic methanogenic archaea. Bio-trickling filter reactors can offer a high specific area for biofilm growth, high density of biomass and are known for high gas to liquid and gas to biofilm mass transfer coefficients. The bio-trickling filter reactors will be filled with innovative and high porous materials for efficient CO2 and H2 uptake.
Firstly, the critical velocity of the porous materials will be assessed. Secondly, the bio-trickling filter reactors will be tested to maximize methanation. Co- and contra- flow of gas will be examined in relation to trickling flow. Parameters such as gas retention time will be monitored towards optimization.