Biological conversion of CO₂ to CH₄ using hydrogenotrophic methanogen in a fixed bed reactor

Abstract

BACKGROUND: Biological conversion of CO 2 to useful carbonic compounds such as methane is a potentially attractive technology for reducing its concentration in the atmosphere. One of the advantages of this technology over chemical conversion is that it requires much lower energy for reduction of CO 2 . In this article, biological conversion of CO 2 to CH 4 using hydrogenotrophic methanogens was examined in a fixed bed reactor inoculated with anaerobic mixed culture from the anaerobic digestor of a sewage treatment plant. RESULTS:Methane formation commenced on the first day of operation of the fixed bed reactor. CO 2 fed to the reactor was reduced with H 2 by hydrogenotrophic methanogens. The feed ratio of CO 2 to H 2 is an important factor in determining the conversion rate of CO 2 . When the feed ratio is 4, methane is produced at the expected rate according to the chemical equation. The CO 2 conversion rate was 100% when the gas retention time was 3.8 h in the fixed bed reactor. CONCLUSIONS:The results show that the fixed bed reactor employing hydrogentrophic methanogens has the potential to be effective in converting CO 2 to CH 4 with a conversion rate of 100% at 3.8 h retention time.

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

“…Firstly, the addition of H 2 to anaerobic digesters of organic matter in order to remove CO 2 from biogas while increasing the production of biomethane Wang et al, 2013) and, secondly, the supply of H 2 and a CO 2 (or biogas) to an exclusively methanogenic bioreactor rich in hydrogenotrophic archaeas (Burkhardt and Busch, 2013;Ju et al, 2008;Kim et al, 2013;Lee et al, 2012;Peillex et al, 1990). Both lines of research found that the barrier to the successful development of the technology on an industrial scale is the gas-liquid mass transfer of H 2 , due to its low solubility (dimensionless Henry's constant, H H 2 = 50 and 55 g=L G =g=L H 2 O at 35 and 55°C, respectively).…”

A Critical Assessment of Microbiological Biogas to Biomethane Upgrading Systems

“…This is, CH 4 is transferred alongside with CO 2 and H 2 from the gas into the liquid phase, reducing the gas to liquid mass transfer of H 2 /CO 2 [22,30], which was found to reduce the volumetric CH 4 productivity tremendously [30]. In this respect, bioreactors other than stirred tank reactors could be considered [9], [41,42]. Furthermore, high volumetric CH 4 productivities are usually demanded for industrial processes.…”

Factors affecting biological reduction of CO2 into CH4 using a hydrogenotrophic methanogen in a fixed bed reactor

“…They are inhabitants of the anaerobic reactor, which has been regarded as an attractive process for the reduction of various types of compounds. Our previous study showed that CO 2 fed to the fixed bed reactor inoculated with anaerobic mixed culture from the anaerobic digestor of sewage treatment plant was reduced with H 2 without organic carbon source [6]. Methane formation commenced on the first day of operation of the fixed bed reactor.…”