Campfires "produce more energy out than energy in" too - the kindling is energy in, but once you've established a chain reaction (no, not an out-of-control chai

Campfires "produce more energy out than energy in" too - the kindling is energy in, but once you've established a chain reaction (no, not an out-of-control chain, but yes a self-sustaining chain) you get warm. Exothermic.