Probably transaction fees? There's no reason a blockchain must be self-funded through proof-of-work mining.

To my understanding, the expected future state of Bitcoin is that the role currently filled by miners will be replaced by transaction processors who take a fee to do the work.

It's not about the mining!!!! Block chain is about having an immutable, non-repudiatable transaction record.

Block chain is a wheel.... guess what, wheels have uses far beyond the Pharaoh's war chariots. Like, you know, bicycles and automobiles. Stop conflating block chain and crypto-currency.

It is about the mining though. The mining is what makes the blockchain immutable. How do you propose making it immutable without that feature?

There are two ways to secure a ledger. Mining, and accountable BFT like Tendermint.