### Biomass Power Generation at Sewage Treatment Facilities and its Development - Case Study of Hita City, Oita Prefecture

### Biomass Power Generation at Sewage Treatment Facilities and its Development - Case Study of Hita City, Oita Prefecture

In April 2012, Hita City, Oita Prefecture, began operating a biomass power generation facility that utilizes methane gas generated from sewage sludge treatment at the city's purification center. The facility uses a high-efficiency micro gas turbine generator manufactured by Sumitomo Heavy Industries, Ltd. with an output of 95 kilowatts and an annual power generation capacity of approximately 810,000 kilowatt-hours. This amount of power generation covered 27% of the entire purification center's annual power consumption, contributing to the improvement of the region's energy self-sufficiency rate. The project was subsidized by the Ministry of the Environment and local government, and the installation of the facility attracted attention as the first of its kind in Oita Prefecture.

The following year, in October 2013, Hita City launched the new Hita City Biomass Recycling Center. At this facility, raw garbage and pig manure from households are processed through methane fermentation, and the biogas generated is used to generate electricity and all electricity is sold. Since the facility was installed, annual energy production has improved, further increasing the energy efficiency of the entire community. This has earned Hita City a reputation as a model renewable energy region.

In the 2020s, however, the facilities began to age, and increased maintenance costs emerged as an issue; in 2023, after considering the cost and efficiency of updating the Biomass Recycling Center, the decision was made to discontinue the facility and the separate collection of food waste. Meanwhile, biomass power generation at the purification center continues, and new initiatives have been launched.

In 2024, Hita City and Kyushu Electric Power Company cooperated to launch a demonstration project to produce liquid fertilizer from sewage sludge and food waste. This fertilizer is expected to contribute to the revitalization of local agriculture and is an important initiative to reduce the environmental burden and realize a recycling-oriented society.

In addition, Hitachi Zosen is involved in the maintenance of the power generation equipment used at the purification center, and efforts are underway to maximize the operational efficiency of the facility. In this way, Hita City continues to expand the use of renewable energy and serve as a model region for waste resource recovery.

These efforts in Hita City continue to provide innovative solutions to environmental problems while aiming to maximize the use of local resources.