There are few studies on the actual power consumption of small-scale sewage treatment plants, and the feasible energy-saving measures are not clear.

　Characteristics of electricity consumption intensity of small treatment plants were summarized using statistical data and estimates. Through hearing surveys at actual small-scale sewage treatment plants, the cause of high power consumption was estimated. Based on these survey results, we examined energy-saving measures.

　Japanese government has declared in October 2020 that Japan will achieve carbon neutrality by 2050. Energy Management Subcommittee on Sewerage, established by National Institute for Land and Infrastructure Management, organized the details of measures that will contribute to achieving carbon neutrality, and estimated the amount of greenhouse gas emissions in FY2050, taking into account the effects of greenhouse gas reduction measures. However, there remains the problem that the actual amount of reduction that sewerage should work on and the priority in the countermeasure fields are unclear because the results of this estimation include external factors due to population decline and changes in the power source composition. Therefore, the effect of external factors was separated and the actual reduction amount (about 3.12 million tons-CO₂ / year) to achieve carbon neutrality was calculated. Then, the priority of the countermeasure field that the development and introduction of the innovative technology should be promoted was examined. It was shown that energy generation, electric power, water treatment (N₂O), sludge incineration (N₂O), fuel, and composting were the highest in this order.