High performance biogas upgrading using a biotrickling filter and Hydrogenotrophic methanogens

This research reports the development of a biotrickling filter (BTF) to upgrade biogas. A bench-scale bioreactor was packed with polyurethane foam (PUF) and inoculated with hydrogenotrophic methanogens enriched from swine waste. H2 and CO2 were fed to the bioreactor at a ratio of 80:20 based on the biological reaction stoichiometry along with inert N2, which served as an internal standard and quantification for effluent flow. Maximum CH4 production rates recorded were as high as 49 m3 CH4 m-3reactor d-1, which is over 9 times faster than for direct injection of H2 to anaerobic digesters and nearly 6 times faster than bioreactors with gas sparging through hollow fiber membranes. The high rates were attributed to the efficient mass transfer and high density of methanogens in the biotrickling filter. The recorded removal efficiencies for H2 and CO2 during this optimal period were 83% and 96%, respectively. CTC/DAPI staining revealed that 67% of cells were live near the gas entrance port, while only 8.3% were live at the exit, suggesting that process optimization could possibly reach even higher biogas upgrade rates. DNA sequencing showed that Methanobrevibacter arboriphilus, a micro-areotolerant methanogen, was the dominant species in the bioreactor.