Optimizing Microbiological Aspects of Archaeal Cultures for Power-to-Methane Trickle Bed Reactors

Microbiological methane production, crucial for biogas plants and power-to-methane applications, often relies on non-defined microbial communities. While this approach offers accessibility, achieving constant, gas-grid-ready quality remains challenging. Limited understanding of these communities complicates issue identification when methane production deviates.

Addressing this, our study - within the scope of the ORBIT II project - explored defined cultures and co-cultures of methanogens for use in a trickle bed reactor. Our primary goal was to characterize and compare a methanogenic co-culture with the respective monospecies cultures. Additionally, we aimed to implement a robust RT-qPCR methodology for analyzing methanogenic co-cultures.

Laboratory experiments focused on a defined methanogenic co-culture with one representative from the order Methanobacteriales and one from Methanococcales, testing them with various gas mixtures reflecting real educt gasses at potential power-to-methane reactor sites like sewage plants. Further, we analyzed the growth and methane production of the cultures in a temperature range from 60-70°C and with varying salts concentrations (NaCl, MgCl2, MgSO4). Last, a method for quantifying the microbial community, optimized for trickle-bed samples through RT-qPCR, was established.

The used archaea demonstrated efficient hydrogen utilization, a critical factor in trickle bed reactors. Even in the presence of small amounts of oxygen, most methanogens thrived and produced sufficient amounts of methane. However, the established co-culture proved more resilient to temperature, oxygen, and ion concentration fluctuations compared to monospecies cultures, therefore enhancing reactor stability. RT-qPCR emerged as a powerful tool for co-culture composition analysis when microscopic methods were impractical.

In conclusion, this study characterized a methanogenic co-culture's advantages and disadvantages, providing valuable insights for its future application in trickle-bed reactors.