"Researchers have discovered that living plants are literally 'green' power source: they can generate, by a single leaf, more than 150 Volts, enough to simultaneously power 100 LED light bulbs"
https://www.sciencedaily.com/releases/2018/12/181212093308.htm
"To extract electricity from trees and convert it into useful energy, researchers built a boost converter capable of picking up as little as a 20 millivolt output and storing it to produce a greater output. By hooking it up to a tree using electrodes, the custom-built device was able to generate an output voltage of 1.1 volts, enough to run low-power sensors."
https://www.livescience.com/5711-electricity-harvested-trees.html
"Children the world over who have tried the potato battery experiment know that plant material can be a source of electricity. In this case, the energy comes from reduction and oxidation reactions eating into the electrodes, which are made of two different metals – usually copper and zinc.
The same effect was thought to lie behind claims that connecting electrodes driven into a tree trunk and the ground nearby can provide a current. But last year Andreas Mershin’s team at MIT showed that using electrodes made of the same metal also gives a current, meaning another effect must be at work. Mershin thinks the electricity derives from a difference in pH between the tree and the soil, a chemical imbalance maintained by the tree’s metabolic processes."
https://www.newscientist.com/article/dn17767-trees-could-be-the-ultimate-in-green-power/
How to Build a 12V Earth Battery Using Just Copper and Soil
