According to the University of Colorado Boulder, breweries go through about seven barrels of water for every barrel of beer produced. All that leftover wastewater can't just be dumped in the sewer – it has to be filtered first, which can be expensive. Now, however, the university says that there may be a new use for the water. It could be used to grow a fungus that's in turn made into "green" battery electrodes.

In lab tests, UC Boulder scientists added Neurospora crassa fungal spores to ordinary brewery wastewater. After the liquid had been shaken and heated for two days, fungus grew within the sugar-rich water.

That fungus was subsequently filtered out and baked at 800 ºC (1,472 ºF) until charred. The resulting carbon-rich material can reportedly be used to produce "one of the most efficient naturally-derived lithium-ion battery electrodes known to date." The leftover water, meanwhile, has already been filtered.

If scaled up to a commercial level, the process could conceivably provide battery manufacturers with a ready-made incubating medium for the fungus, while reducing the amount of wastewater that brewers have to treat.

Study co-authors Tyler Huggins and Justin Whiteley have filed a patent on the technology, and established the startup company Emergy to develop it further.

A paper on the research was recently published in the journal Applied Materials & Interfaces.