Right I have cunning plan... If we cant spend money on reforming people we might as well do the following.
What you do is put all these prisoners on exercise bikes with a dynamo attached to generate electricity. The amount they cycle per day is proportional to the severity of the crime committed.
An average person generates 150W of power cycling for 1hr. Prison population is around 97000 and cycling for 7.5hrs a day (37.5hrs a week). 97000*150W*37.5*52= 28.378GW per year, thats enough to power more than 10000 houses for a full year and we have the chance to find the next Bradley Wiggins saving money from Team GBs budget.
Or we could go total dystopian future and use their thermal energy (Matrix style), 105W per hour so about 2.5kW per day * 97000 = 244MW per day or just short of 90TW per year or roughly 1/3 of the UK entire electricity consumption per day. Just need to feed them a low cost high energy sugar and away we go.
See big problems require innovative solutions.