I’m not sure how well these work, but apparently the NoPoPo (no pollution power) batteries can be charged by peeing, yes peeing into them.  I’ll stick to my Enloops thank you very much seeing as you can only recharge them 2 to 5 times.

The NoPoPo batteries are rechargeable via a variety of liquids, including water and urine, injected into the battery chamber with a pipette. A mixture of magnesium and carbon reacts with the liquid and produces power up to 500 mAh in the case of an AA-size battery. The batteries come in AA and AAA and retain their charge for up to 10 years. However, they can be recharged only a limited number of times (2 to 5 times on average).

Available here for $15

[ShinyShiny]