The biocompatibility of converting CO2 from scrubbed flue gas was tested with the same method as for the testing the biocompatibility of converting scrubbed CO2 from pure bottled gas streams. MDEA concentrations of 30 mM and 60 mM were applied for the flue gas scrubbing based on the results from the methane productivity in the previous experiments. The flue gas was supplied from a 625 kW biogas engine and generator (Jenbacher JMS 312 GS-B.L), where a fraction of the exhaust flue gas was redirected from the chimney to the aqueous amine solutions for CO2 scrubbing. The aqueous amine solutions were kept at a temperature of 48°C with a water bath to maintain methanation reactor temperature and reduce the solubility of O2, since the dissolved oxygen could interfere with the anaerobic environment that was required for the methanogenic archaea to sustain the activity. The dissolved oxygen concentration was measured for each flue gas batch reactor before and after the operation with an optical dissolved oxygen probe (Vernier Go Direct®).