Japan pioneers osmotic power with world's second plant where salt water meets treated sewage water to create pressure

The plant, operated by the Fukuoka District Waterworks Agency, marks Japan as only the second country in the world to deploy this technology after a Danish company pioneered it in 2023, according to Kyodo News. Local officials and experts present the project as a breakthrough for renewable energy that can run around the clock, unaffected by weather or sunlight, and without emitting carbon dioxide. “I feel overwhelmed that we have been able to put this into practical use. I hope it spreads not just in Japan, but across the world,” said Akihiko Tanioka, professor emeritus at the Institute of Science Tokyo, in comments to Kyodo News.

Beneath its understated exterior, the Fukuoka facility relies on a process known as salinity gradient power. Treated sewage water and highly concentrated seawater are separated by a special permeable membrane, triggering osmosis as water molecules move toward the higher salinity side. The resulting water pressure spins a turbine, which in turn powers a generator.

The plant is expected to generate approximately 880,000 kilowatt-hours of electricity annually, according to the Fukuoka District Waterworks Agency. That energy will directly support a local desalination plant supplying fresh water to Fukuoka City and neighboring areas—tying the renewable energy project closely to local water infrastructure.