Distillation is pretty expensive, energy-wise, and if you can't run continuously [e.g. if you're trying to use cheap intermittent renewables] you lose energy in the cooling-and-reheating cycles.

I have yet to see a significant source of usable "waste" heat that's not already being used for something else. Low-grade heat isn't helpful--you generally need reasonably high temperature differentials in order to power large-scale industrial processes.

[Disclosure: I've invested in Prometheus Fuels, but don't speak for them.]

>Distillation is pretty expensive, energy-wise,

Moonshining is less than 400 KJ per kg of source, i.e. about 1.5 KWh per kg of ethanol produced from 15% ethanol/water source. Given that one can use waste heat from almost any other industrial process the real monetary cost is way less than the cost of electrical 1.5 KWh.

>I have yet to see a significant source of usable "waste" heat that's not already being used for something else. Low-grade heat isn't helpful--you generally need reasonably high temperature differentials in order to power large-scale industrial processes.

Moonshining is 78 C degree - such cheap waste heat sources are plentiful exactly because it is hard to use for almost anything else.

>you lose energy in the cooling-and-reheating cycles.

not an issue for a 78 C process - basically like your water boiler, takes minimum of thermal isolation.

Well that answers my question about crypto waste heat and useful work.

How were you able to invest, if you don't mind me asking?

I've often wondered if I could justify a crypto mining rig if I used the waste heat for something, literally anything, useful. The tech is interesting and I want to for the sake of "doing something cool" but the environmental cost has me iffy on ever trying.

Heat your house?

https://www.newscientist.com/article/mg22530072-800-the-comp...

Earthship, heatpump, and this... getting pretty close to a dream house TBH.