Could zombies reduce our need for foreign oil?

Okay, stay with me here. Zombie apocalypse hits, but we keep it under control. We quarantine all the zombies to prevent infection. Zombies don’t get tired—they can walk forever (as was clearly shown in the book World War Z).

So what if you put the zombies on treadmills, and then hang brains in front of them just out of reach. They start walking, the treadmill moves, and then you harness the energy of the treadmill to add to the power grid.