This research worked on the measure against CO 2 reduction according to the characteristics of the area for the Kanazawa seaside area in Yokohama city. This area consists of a collective housing complexes and a minor scale industrial complex, and also locates a waste incineration plant, a wastewater treatment plant, and a sludge treatment facility. Having been chosen as a measure with the large amount of CO 2 discharge reduction, it is the system which feeds into an incinerator the methane gas by carrying out mixed digestion of the kitchen garbage together with sewer sludge, and supply heat from a waste incineration factory through the transmission line. However, since this system has large initial cost for construction of transmission line, marginal abatement cost (MAC) for CO 2 emission reduction is very as large as 166.16 [USD/CO 2 ]. Then, when the pay-back year of the transmission line was changed from 20 years to 31.5 years which is equivalent to 70% of legal durable years, MAC was reduced to 104.40 [USD/CO 2 ]. Moreover, when Non Energy Benefit (NEB) by system introduction, such as job creation and an environmental improvement of the area, was taken into consideration, MAC was greatly reduced to -124.22 [USD/CO 2 ].