초록
<P><B>Abstract</B></P> <P>Biogas is composed of energetically useable methane (CH<SUB>4</SUB>) ranging from 50 to 70% and carbon dioxide (CO<SUB>2</SUB>) taking up 30–50%. To upgrading biogas to biomethane for better exploitation of its energetical potential, many different physico-chemical processes are commercially applied. Besides these methods, biological methods for the conversion of CO<SUB>2</SUB> with electrolytic H<SUB>2</SUB> to biomethane based on the activity of hydrogenotrophic methanogens are also currently being researched. This study deals with the adaptation of anaerobic culture to H<SUB>2</SUB> and CO<SUB>2</SUB> as substrates under thermophilic and mesophilic conditions. Thermophilic cultures initially showed slower adaptation, but CO<SUB>2</SUB> conversion efficiency was finally by 12.7% higher compared to the mesophilic culture under the same conditions of the H<SUB>2</SUB> loading rate. Thermophilic conditions were favourable also for homoacetogens producing higher concentration of acetate from CO<SUB>2</SUB> and H<SUB>2</SUB> under thermophilic condition compared to mesophilic condition in the excess of H<SUB>2</SUB>. Maximum capacity of the used thermophilic suspended biomass for bioconversion of CO<SUB>2</SUB> was the H<SUB>2</SUB> loading rate 2 L/(L.d) resulting in CO<SUB>2</SUB> bioconversion efficiency of 84% (median) in contrast with 40% (median) for mesophilic culture. The system was limited by the concentration of biomass round 4 g/L.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biogas obtains 30–50% energetically unusable CO<SUB>2</SUB>. </LI> <LI> Bioconversion of CO<SUB>2</SUB> with H<SUB>2</SUB> to CH<SUB>4</SUB> increases energy potential of biogas. </LI> <LI> Hydrogenotrophic methanogens are able to use energy conserved in electrolytic H<SUB>2</SUB>. </LI> <LI> Hydrogenotrophic methanogens are better adaptable under thermophilic conditions. </LI> </UL> </P>