There is a new method to create waste backed crypto with anaerobic digestion. This is an unlimited resource. You can convert waste and sewage to electricity in these new plants and then sell the electricity with Energy Web Token (EWT). Send a private message for more details if you are interested.
Sorry to say but this never works, few projects since two years back have introduced a waste backed crypto tokens and they failed or turn scam, it seems this is another example of use case that is not really needed on the blockchain