Soil and technology. So much technology comes from our exploration, and mining, the soil for its goodness.
I have taught soil laboratories and done demonstrations where we used a clay suspension, think of a clay mud bath that is a little to runny, to power a small light bulb. Just takes a copper wire and a zinc electrode separated in a beaker of the suspension.
It is a curiosity to some but it helps to link together the concepts of bacterial electron transport chains in their cell wall, electron movement in soil, and electron movement to power lights and do other work.