[kardos]

If the waste heat could be harvested and used for another purpose (district heating? cooking?) that would more or less curtail the waste, yes?

[xyzzyz]

If you could do that so easily, you'd already do it in aluminum plants, which are kinda like bitcoin already -- electricity in, aluminum out. Suffice to say, it doesn't really happen.

[mikeash]

It would help a bit, but electric resistive heating is not very efficient.

[jakeinspace]

Only problem is the second law of thermodynamics but sure, why not.