Biological CO₂ fixation in up-flow reactors via exogenous H₂ addition

Area of Science:

• Biotechnology
• Environmental Science
• Chemical Engineering

Background:

• Greenhouse gas emissions reduction is a global priority.
• Gas fermentation offers a sustainable route for producing biofuels and chemicals.
• Biological conversion of carbon dioxide (CO2) and hydrogen (H2) is crucial for carbon capture and recycling.

Purpose of the Study:

• To evaluate the performance of two up-flow reactors for CO2 and H2 assimilation.
• To investigate the impact of reactor design on gas transfer and utilization.
• To identify key microbial communities involved in the biomethanation process.

Main Methods:

• Comparative analysis of two up-flow reactor configurations.
• Process monitoring of gas-liquid hydrogen transfer and gas utilization.
• High-throughput 16S rRNA sequencing for microbial community analysis.

Main Results:

• Reactor design significantly impacts gas-liquid H2 transfer.
• A reactor packed with Raschig rings achieved 81% CH4 content with enhanced gas utilization.
• Absence of packing material resulted in limited biomethanation, underscoring the role of packing.

Conclusions:

• Packing material, specifically Raschig rings, plays a vital role in enhancing the performance of up-flow reactors for gas fermentation.
• Optimized reactor design is key to efficient CO2 and H2 assimilation for methane production.
• Methanothermobacter methanogens were identified as the dominant microbial species in the reactor.