LOL I can see it now, hordes of miners powering their rigs by bicycle! It would be really cool to be able to be green while being able to have Ghps but I just don't see it possible.
The best bicycle generator I've found is "kit" (bike not included) producing 300W for $400.
http://www.amazon.com/Bicycle-Generator-Watts-Pedal-Dynamo/dp/B003GJL6GO (no affiliate link). So we'll need one cyclist per small rig, full time with no bathroom breaks. I think its scalable.