Comparison and Gas Loading Impact on Counter- and Concurrent Trickle-Bed Reactor Configurations for Ex-Situ Biomethanation

In this work, the two different configurations (counter- and concurrent) of laboratory scale trickle-bed reactors for ex-situ biomethanation were studied under continuous operation. Reactors operating at thermophilic conditions (50°C) were fed with H 2 and CO 2 (ratio 4:1) while cow manure used as liquid phase and source of nutrients for microbiota. Studies were performed at the gas loading rate ranging from 10 m 3 /m 3 /d to 30 m 3 /m 3 /d. The counter-current configuration performed better and had a higher stability compared to concurrent configuration. It achieved 96.1 ± 2.5% of CH 4 at gas loading 10 m 3 /m 3 /d compared to 86.4 ± 3.3% of CH 4 in concurrent at the same loading. At gas loadings >15 m 3 /m 3 /d, the concurrent configuration had unstable performance (decreasing CH 4 content), while the counter-current reactor exhibited stable performance even at the highest studied loading (30 m 3 /m 3 /d), with 68.5 ± 2.5% of CH 4 . The hydrogenotrophic methanogens such as Methanobacterium (45.7-64.9%) and Methanothermobacter prevailed in both configurations.