| Abstract | The present study investigates, optimizes and compares the conversion of carbon monoxide (CO) and syngas (CO/Hz/C02, 40/40/20, and 20/20/10, v/v) to renewable natural gas (RNG) in two types of reactors, trickle-bed reactor (TBR) and fluidized bed reactor (FBR), highlighting their respective advantages and disadvantages. The comparison considered various aspects of reactor operation efficiency with regards to the specific roles of the different microbial trophic groups for RNG production. Overall, TBR results indicate good conversion efficiencies (up to 97%) and a relatively constant stoichiometry-based CH4 yield (88-100%), for CO partial pressures lower than 0. 5atm. regardless of the operational condition tested. Once the biofilm was sufficiently developed, a maximum CO conversion activity of 37 mmolCO.g- 1 volatile suspended solid (VSS). d-1 was achieved. In FBR, restricted mass transfer and absence of attached biomass growth limited the overall reactor efficiency. Only 10% of initial biomass concentration was recovered at the end of the test. The reactor was operative at higher CO partial pressure with non-diluted syngas but the maximum efficiency obtained under stable operating conditions was barely 82-85%. During the reactor operation, methanogenic, hydrogenophilic, acetoclastic and carboxydotrophic specific activities varied in function of substrate composition, biofilm type and structure. |
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