At rest, the human body generates an average of 100 watts of output. During sports activities, it reaches 300 to 400 watts
Okay. So we have a thousand inmates, and let’s say we can keep them moderately physically active half the time (may need to swap out inmates as they die of exhaustion). Obviously they will be producing value with their slave labor but that is irrelevant. So that’s
1000x200=200,000W or 200kW
200x24=4800kWh produced per day
I’m finding varying data on the kWh needed to mine a Bitcoin, but it seems like 250,000 is semi accurate.
4800/250,000=0.0192
So we are getting 0.0192 Bitcoin per day (BTC/d), which means with the proper equipment hooked up to these prisoners we can generate about $1300 worth per day. Obviously this value will fluctuate, but if we time our sales correctly we can make it worth even more.
You just take the people who would be served by the libraries—especially poor and homeless people—and you "serve" them with the jail instead. Problem Solved™.