Urine-powered cellphones I. A. Ieropoulos et al., Phys. Chem. Chem. Phys. (2013)

According to scientists at the University of the West of England in Bristol, microbial fuel cells using human urine can directly power a cellphone battery -- something these researchers first demonstrated in 2011, Science reported.

As the urine cascades through a series of fuel cells, hungry bacteria consume it and release electrons, which generate an electrical current. But pee-powered conversations would have to be short -- after 24 hours of charging, a Samsung phone only stayed alive for 25 minutes.