**7. Conclusion**

The atmospheric carbon dioxide originated from petroleum and coal is required to be completely isolated from the ecological material cycles. The carbons in the ecological system are accumulated as the organic compounds in the organisms and as the carbon dioxide in the atmosphere, which is cycled via the photosynthesis and respiration, especially, plants are the biggest pool for carbon storage. However, the forest and plant-habitable area has been decreased continuously by human activities.

The cultivation of cyanobacteria and single cell algae with solar energy may be the best way to isolated effectively carbon dioxide from atmosphere but is possible in the water pool-type reactor located in the plant-habitable area. In other words, the forests or grass lands may be replaced by the water pools, by which the effect of carbon dioxide fixation has to be decreased. The cyanobacteria and algae can be cultivated in the bioreactor using lamp light operated with electric energy that is generated from solar cells, for which the solar energy has to be converted to electric energy and then converted again to the light energy. These phototrophic microorganisms have been studied actively and applied to produce nutrient sources and pharmacy. The goal for cultivation of the phototrophic microorganisms is to produce the utilizable materials but not to fix carbon dioxide like the agricultural purpose.

The carbon compounds of the organic nutritional compounds contained in the sewage wastewater are the potential carbon dioxide, which may be the useful medium for cultivation of the mixotrophic bacteria capable of fixing carbon dioxide. The maximal balance of anabolism to catabolism is theoretically 0.4 to 0.6 in the mixotrophic bacteria growing with organic carbons as the energy source, in which the carbon dioxide can't be the source for both anabolism and catabolism; however, the balance can be changed by the external energy like the electrochemical reducing power. In the condition with both the organic carbons and the electrochemical reducing power as the energy source, the balance of anabolism to catabolism may be increased to be higher than 0.4 due to the carbon dioxide assimilation that is generated in coupling with the redox reaction of biochemical reducing power electrochemically regenerated. The electrochemical reducing power can induce regeneration of NADH and ATP, by which both the assimilation of organic carbon and carbon dioxide into bacterial structure compounds can be activated. The goal of cultivation of bacterial cells using the cylinder-type electrochemical is to assimilate the atmospheric carbon dioxide to the organic compounds for bacterial structure without the combustion of fossil fuel and without production of metabolites. Some metabolites that are methane and acetic acid can be generated by the strict anaerobic bacteria under anaerobic hydrogen-carbon dioxide atmosphere but not useful for industrial utility owing to the cost for production. Meanwhile, the methane and acetic acid produced from the organic compounds in the process for treatment of wastewater or waste materials may be useful as the by-product for the industrial utility. The cell size and structural character of bacteria permits to put directly the bacterial cells in the empty petroleum well without any process, by which the atmospheric carbon dioxides are returned to the original place.
