The city announced today that sewage will be converted into electricity at the Kailua Wastewater Treatment Plant — enough electricity to save the city $15 million over 15 years. The process is called co-generation.

“This is a great example of an innovative green energy project that makes solid sense for our community,” Mayor Peter Carlisle said in a press release. “It will provide a new source of clean electricity that saves money.”

Sewage-to-energy is the same type of technology that the Honolulu City Council has been pressuring Carlisle to consider for the Sand Island plant instead of the fertilizer-pellet-producing system in place there now.

During budget deliberations, Carlisle’s administration said it intended to install the co-generation technology at other facilities, and now it’s making strides in that direction.