A feasibility study on the bioconversion of CO2 and H2 to biomethane by gas sparging through polymeric membranes

Biogas upgrading and utilization: Current status and perspectives

“…(3) (Martin et al, 2013) where r t is the H 2 gas-liquid mass transfer rate (L/(L Reactor .day), 22.4 is the corresponding volume that occupies 1 mol of gas at standard condition of temperature and pressure (L/mol), k L a is the gas transfer coefficient (day − 1 ), H 2g is the H 2 concentration in the gas phase (mol/ L), and finally H 2l expresses the dissolved H 2 in the liquid phase (mol/ L). Therefore, it is obvious the H 2 gas-liquid mass transfer rate is proportionally correlated with the k L a, which in turn is dependent on specific operational parameters such as the gas recirculation flow (Guiot et al, 2011;Kougias et al, 2017b), the reactor configuration (Bassani et al, 2016;Kougias et al, 2017b), the installed diffusion device (Bassani et al, 2017;Díaz et al, 2015;Luo and Angelidaki, 2013b) and the stirring intensity Angelidaki, 2013b, 2012). A number of research publications are proposing different novel concepts for increased biomethanation efficiencies.…”

“…The limiting step in hydrogen assisted methanogenesis is not always the biological conversion catalyzed by the microbial species but more often the H 2 diffusion in the liquid medium (Díaz et al, 2015). In the presence of high H 2 concentrations, the hydrogenotrophic archaea consume H 2 for CH 4 production instead of using it for microbial growth (Reeve et al, 1997).…”

Long-term open circuit microbial electrosynthesis system promotes methanogenesis

“…Moreover, the strong presence of produced hydrogen during the first days after reconnection could also favor the proliferation of Methanobacteriaceae. Here it is important to remember that hydrogenotrophic methanogenesis is energetically more favorable than homoacetogenesis in the presence of hydrogen gas, and thus hydrogenotrophic methanogens might be outcompeting homoacetogens [21] . De-spite the operational conditions (temperature, pH, conductivity, etc.)…”

“…In this sense, up to 10 different electromethanogenic routes have been described to be able to individually or simultaneously occur in mixed culture biocathodes [22] . Thus, it might be possible that Syntrophic Acetate Oxidizers (SAO) such as Clostridium [25] could be consuming acetic acid and producing hydrogen, which in turn would explain the lack of acetic acid observed in the medium [21,26] . Although hydrogen production from acetate is thermodynamically unfavorable, SAO bacteria are in a syntrophic relationship with the H 2 -consuming methanogens, making the whole process thermodynamically favorable [26,27] .…”

Biological hydrogen methanation systems – an overview of design and efficiency

“…While carrying out experiments, it is key to determine k L a for H 2 , CO 2 and CH 4 ; H 2 being the most important due to the necessity of the gas for biological methanation, and its inherent poor solubility. This data is scarce in the literature, but some studies have investigated similar concepts [15,48,58,61].…”