Provided is a treatment system whereby a wet organic waste can be effectively treated and CO2 produced in the course of the treatment can be immobilized to thereby contribute to the reduction of CO2. The treatment system is characterized by including microbiologically fermenting a wet organic waste in a fermentation device, combusting in a combustion furnace a fermented material obtained from the fermentation device and, at the same time, supplying to the combustion furnace a fermentation gas produced by the microbiological fermentation treatment in the fermentation device, and then recovering and immobilizing CO2 in a hot exhaust gas produced by the combustion treatment in the combustion furnace.