As it's known for many years, various exhaustible resources have been used to trade or to make transactions. This has not changed until today. As you know, Bitcoin and its mining requires tons of energy that can not even be counted. There is no doubt about it, however, for the use of ordinary currencies we need paper and metallic alloys which, as we know, are not infinite and may also end sometime. It is worth finding a golden mean in using all the resources of Mother Earth.