초록
Carbon dioxide (CO<SUB>2</SUB>) is the main greenhouse gas; hence, processes are needed to remove it from the environment. Here, CO<SUB>2</SUB> was used as the substrate to generate methane (CH<SUB>4</SUB>) by using enriched methanogens after anaerobic enrichment of waste activated sludge (WAS); therefore, we demonstrate that methanogens from WAS have significant potential for converting the greenhouse gas CO<SUB>2</SUB> into the fuel methane. Methane production was found to increase 70 fold by active methanogens in the enriched methanogens culture after 3days in the presence of H<SUB>2</SUB> and CO<SUB>2</SUB>. Throughout the process, CO<SUB>2</SUB> was completely consumed after 4days of incubation in the vials after sparging with a mixture of H<SUB>2</SUB> and CO<SUB>2</SUB>, resulting in significant biological CO<SUB>2</SUB> sequestration by methanogens. Using a mixture of H<SUB>2</SUB> and <SUP>13</SUP>CO<SUB>2</SUB>, we also demonstrated that the methane produced is due to the utilization of CO<SUB>2</SUB>. Microbial community studies via by quantitative real time PCR (qRT-PCR) indicate the dominance of archaea in the enriched methanogens culture of WAS. Archaeal community studies of the enriched methanogens via high-throughput 16S rRNA sequencing also showed that the archaea consist mainly of hydrogenotrophic and aceticlastic methanogens such as Methanobacteriaceae, Methanospirillaceae and Methanosarcinaceae spp. which are actively grown in H<SUB>2</SUB> and CO<SUB>2</SUB>. We envision that CO<SUB>2</SUB> gas from power plants can be directed to enriched methanogens of WAS to prevent release of this greenhouse gas while generating a useful biofuel (methane) or other valuable products using this single carbon atom.