The conversion of fuel into electricity into PoW hashes acts like a 'battery charger' for putting intrinsic value into each unit of a cryptocurrency.
I contend that complaining about PoW algorithms 'wasting' energy is roughly the equivalent of complaining about the first combustion engines wasting fuel. It's a subjective argument that ignores the value added to the broader economic and financial ecosystems.
Good topic to debate!
RE: Why Bitcoin is not sustainable and a better alternative to the proof-of-work algorithm. Part I