[nctr]

There are alternatives, Proof of Stake for example, or gridcoin, where the computing power to "mine" gridcoin goes towards scientific projects via BOINC.

[oafitupa]

Yeah, there are also bottle caps which can be used as currency!

But seriously, don't call those "alternatives" if they are not secure. There is no known replacement for PoW.

[nctr]

Why does Proof of Stake not work in your opinion?