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Although prisons are ostensibly intended as places where convicted criminals can pay their debts to society, confinement behind bars rarely yields anything other than the punishment alone. But now, thanks to an innovative new initiative underway at a correctional facility in Brazil, prisoners are being given the chance to slash their sentences while bringing a bit of light into the world, literally -- by producing the electricity used to power street lamps.

According to Jornal Nacional, Brazil's Santa Rita do Sapucaí prison, following the suggestion of a local judge, recently installed electricity-generating stationary bikes as part of a plan to keep inmates active while letting them contribute to a greater good.

For every 16 hours spent pedaling to charge a battery connected to the bike, prisoners of good standing will shave a day off their sentences. The energy will then be used to power streetlights in the city that might otherwise be dark, making the community a safer place at night for everyone.

Using the bikes isn't mandatory, but when their benefits are as win-win, there's no reason it needs to be. "I was a little chubby," says one inmate. "I've lost about nine pounds [riding the bikes]."

Given the success of the program so far, the prison plans to add even more power-generating bikes which will go even further to reduce sentences, waistlines, electricity bills, and carbon emissions -- all while making the world a brighter place, in more ways than one.