Microbial Resilience in Flexible Ex Situ Biomethanation of H2/CO2

Ex situ biomethanation allows the conversion of CO2 and H2 produced from surplus electricity to CH4 . The flexibility of the process was recently demonstrated, however, the impact of substrate starvation on the microbial community remains unknown. Here, we tackle this question by investigating the effect of different starvation events on the microbial community originating from two different inocula. Bioreactors were operated under regular fed batch mode, feeding without shaking, and feeding after 7, 14, and 21 days of starvation. Sludge from a paper industry wastewater treatment plant (WW) and from a plug flow reactor digesting maize silage and manure (PF) were used to study the role of the inoculum in the flexibility of the process. In summary, we showed that flexible biomethanation with complex microbiota is possible and the microbial community successfully survived different starvation events due to microbial resilience. The wastewater inoculum was the most effective and it provides foundation to further investigate a concept of biogas upgrading in wastewater treatment facilities.