In Situ Biogas Upgrading in a Randomly Packed Gas-Stirred Tank Reactor (GSTR)

Giuseppe Lembo, Silvia Rosa, Antonella Marone () and Antonella Signorini
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Giuseppe Lembo: Biotechnological Processes for Energy & Industry Laboratory (PBE), Department of Energy Technologies and Renewables, ENEA, Casaccia R.C., 00123 Rome, Italy
Silvia Rosa: Biotechnological Processes for Energy & Industry Laboratory (PBE), Department of Energy Technologies and Renewables, ENEA, Casaccia R.C., 00123 Rome, Italy
Antonella Marone: Biotechnological Processes for Energy & Industry Laboratory (PBE), Department of Energy Technologies and Renewables, ENEA, Casaccia R.C., 00123 Rome, Italy
Antonella Signorini: Biotechnological Processes for Energy & Industry Laboratory (PBE), Department of Energy Technologies and Renewables, ENEA, Casaccia R.C., 00123 Rome, Italy

Energies, 2023, vol. 16, issue 7, 1-17

Abstract: This study evaluated different strategies to increase gas–liquid mass transfer in a randomly packed gas stirred tank reactor (GSTR) continuously fed with second cheese whey (SCW), at thermophilic condition (55 °C), for the purpose of carrying out in situ biogas upgrading. Two different H 2 addition rates (1.18 and 1.47 L H2 L R −1 d −1 ) and three different biogas recirculation rates (118, 176 and 235 L L R −1 d −1 ) were applied. The higher recirculation rate showed the best upgrading performance; H 2 utilization efficiency averaged 88%, and the CH 4 concentration in biogas increased from 49.3% during conventional anaerobic digestion to 75%, with a methane evolution rate of 0.37 L CH4 L R −1 d −1 . The microbial community samples were collected at the end of each experimental phase, as well as one of the thermophilic sludge used as inoculum; metanogenomic analysis was performed using Illumina-based 16S sequencing. The whole microbial community composition was kept quite stable throughout the conventional anaerobic digestion (AD) and during the H 2 addition experimental phases (UP1, UP2, UP3, UP4). On the contrary, the methanogens community was deeply modified by the addition of H 2 to the GSTR. Methanogens of the Methanoculleus genus progressively increased in UP1 (47%) and UP2 (51%) until they became dominant in UP3 (94%) and UP4 (77%). At the same time, members of Methanotermobacter genus decreased to 19%, 23%, 3% and 10% in UP1, UP2, UP3 and UP4, respectively. In addition, members of the Methanosarcina genus decreased during the hydrogen addition phases.

Keywords: biogas recirculation; biomethane; gas-stirred tank reactor; thermophilic anaerobic digestion; in situ biogas upgrading; microbial community; H 2 gas mass transfer; packed reactor; hydrogenotrophic methanogenesis (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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