Machinery maintenance and repair is good. Welding is good. Building is good and you can make a case for fencing. The others, not so much. 

As for food supplies, I'm not a particularly big fan of governmental vertical integration, or of governments using cheap labour to compete with artisanal cheese makers.

I'd suggest that any of the trades would be preferable, even if the programme only got as far as the 'helper' level - carpenter's helper, electrician's helper, etc. The article mentions solar panel installation. One problem is that such a high proportion of the prison population have serious mental and physical disabilities.