Research

Syngas biomethanation by mixed microbial consortia in trickle bed reactors

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Abstract

The devastating impacts of climate change on our societies are currently more evident than ever. As a result, a change towards renewable energy economy is urgent and it can only be achieved through carbon sequestration and recycling. Syngas is a byproduct of biomass gasification and several industrial activities. Its high energy and carbon content due to its constituents (CO, H2 and CO2) render it an important substrate for the production of biofuels. The conversion of syngas to methane is an attractive option because of the high storage capacity of the natural gas grid. The main advantages of the biological conversion of syngas to methane over the Sabatier process are the low infrastructure cost, the mild temperature and pressure, the negligible cost of the catalyst (microbes) and the fact that there is no demand for a fixed H2/CO ratio. On the other hand, the major bottleneck is the low mass transfer rate of CO and H2 to the water based media. It has been reported, that trickle bed reactors (TBRs) provide higher gas to liquid mass transfer rates compared to the conventional stirred tanks and bubble columns and, thus, they constitute an interesting solution to the main challenge of syngas fermentation [1]. The aim of this study was to assess the efficiency of syngas biomethanation by mixed microbial consortia under mesophilic and thermophilic conditions in TBRs, maximize the concentration of methane in the gas outlet with additional H2 supply and examine the scaling up potential of the process.