Researchers at Stanford University recently developed a small battery that harnesses “blue energy” by mixing seawater from Half Moon Bay and wastewater effluent from Palo Alto. The authors of the study that generated press around the world say that the technology could potentially power coastal wastewater treatment plants in the future.

The battery could function anywhere that saltwater and freshwater mix, so Craig Criddle, a civil and environmental engineering professor at Stanford, suggested the technology could be used at coastal treatment plants, where effluent is sometimes flushed into the ocean.

Saline, the source of blue energy, is found in wastewater at levels similar to that found in freshwater, making treatment facilities a viable testing ground for the technology. In that way, the batteries wouldn’t require fresh water to operate.

Kristian Dubrawski, a study co-author, said researchers chose Half Moon Bay to collect water simply because it was the closest ocean access point to Stanford’s Palo Alto campus.

He added that the potential system would be better served close to the ocean so water would not have to be pumped to the treatment facility.

Timothy Costello, the supervisor of treatment at Sewer Authority Mid-coastside, said the project isn’t necessarily feasible at the Half Moon Bay facility because the effluent pipe is 2,200 feet from the ocean, making it challenging to place the battery where saltwater and wastewater mix.

Dubrawski said researchers need more time to improve the battery’s power density. Right now, a battery that could capture all the blue energy would be “too big.” He noted that building a facility to host a massive battery on the coastline would be challenging.

“It would definitely have some hurdles to overcome,” Costello added.

Still, the technology could have important implications for renewable energy. Researchers believe the battery,  when scaled up, could make coastal treatment plants energy-independent, cutting electricity use and protecting against blackouts.

More than 15 million homes could be powered by theoretically recoverable energy from coastal wastewater treatment plants, according to a Stanford press release. 

“It’s just a matter of time before someone tries to commercialize it,” Dubrawski said. 

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