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

BACKGROUND: Biological conversion of CO2 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 CO2. In this article, biological conversion of CO2 to CH4 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. CO2 fed to the reactor was reduced with H2 by hydrogenotrophic methanogens. The feed ratio of CO2 to H2 is an important factor in determining the conversion rate of CO2. When the feed ratio is 4, methane is produced at the expected rate according to the chemical equation. The CO2 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 CO2 to CH4 with a conversion rate of 100% at 3.8 h retention time. Copyright © 2012 Society of Chemical Industry