The heat recycling argument is weak, imho. As long as mining is profitable, miners can perfectly not bother using or recycling heat. That's what many industries do. They often don't give a crap about their waste products, as long as their main activity generates money. That's one of the main reason why pollution exists, imho.
... if you're mining indoors in a cool climate you're already recycling 100% of the heat generated. Without even trying.
Or you could heat your hot tub and have a pretty good crack at a Darwin Award - depending on the implementation, of course.
