PROBLEM TO BE SOLVED: To provide a technique that can reduce carbon dioxide of a large capacity by using microalgae that carry out photosynthesis. ! SOLUTION: A sewage treatment facility 1 that includes: a cogeneration apparatus 2 that exhausts exhaust gas E including carbon dioxide; an aeration tank 3 that aerates treated sewage W; and a sludge collection tank 5 that recovers sludge S2 in the treated sewage W is used, in a state in which sun light T enters into the treated sewage W in the aeration tank 3 and the exhaust gas E is fed, microalgae 8 that perform photosynthesis are cultured in the treated sewage W, the sludge S2 that contains the cultured microalgae 8 is recovered, the recovered sludge S2 is methane-fermented by a methane fermentation apparatus 9 to be converted into biogas fuel B, and carbon dioxide is reduced. ! COPYRIGHT: (C)2013,JPO&INPIT
