This may soon be possible. Researchers from Bristol Robotics Laboratory, a collaboration between the University of the West of England and the University of Bristol, were able to pee on microbial fuel cells (MFCs) to create enough electricity to charge a Samsung phone.
So far, MFCs have only been used to generate small amounts of electricity for short charge and discharge cycles. This if the first time enough energy has been captured to directly charge a battery."
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