in situ v. ex situ biogas upgrading. Comparison of In Situ and Ex Situ microbial biogas upgrading communities, with hydrogen (IS, ES) and CO2 (ES) injection

This study compares the upgrading communities between in situ and ex situ operation during increasing flow rates of H2 and CO2, showing that the presence (in situ) or absence (ex situ) of feedstock strongly delineates these communities. This in turn governs community response to rates of H2 supply, with in situ communities showing a far greater susceptibility to inhibition, population flux, and displacement of methanogens (Methanothermobacter). In comparison, ex situ upgrading communities saw little change at much higher H2 flow rates, and instead encouraged larger populations of closely related methanogens (Methanobacterium). These large ex situ hydrogenotrophic populations were significantly associated with smaller, ‘satellite’ populations of hydrogen-producing bacteria, indicating a thermophilic upgrading community centred on biogas metabolism.