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
I hadn't seen a good thing to come out from the energy crypto projects yet. Most of those project has a very novel idea but fell short or turn into scams because they don't work in real life. Unrealistic take on how to utilize blockchain for fossil fuel or renewable energy. Recycle waste and turn it into electricity is cost a lot of money to make, the electricity output is low and not a primary goal when operating a waste recycling plant. I don't know about sewage but the hydro dam still the most efficient for utilizing any fluid, water-like material.
theres few that try simillar to this idea and they are not consistent or not serious enough thats why they fail but if many teams and minds will try again to create a serious version i think they will succeed the longer they try .
and why would it be too costy when we are recycling ? recycling supposed to be free of charges except when they are going to market this project online because they are going to use blockchain/cryptos on it .