The cost of government services to citizens during Japan's long-term economic depression poses a challenge for local governments. To ease the burden of running costs of sewage treatment at the local government level, a waste sludge reduction trial was performed in a real-scale plant by postponing sludge withdrawal from the plant. Sludge reduction was also observed in a small-scale sludge-reduction process. Approximately 30,000 USD of the sludge disposal cost was saved by postponing sludge withdrawal from the plant. Sludge reduction reached approximately 35 %. In terms of CO2 emissions related to SDGs (Sustainable Development Goals), an 8,000 kg reduction in emissions was observed owing to reduced waste sludge incineration in the sludge reduction trial described in this study.