Why doesn't activated charcoal spontaneously combust?

I was reading an article on HowStuffWorks about AC FOX, a new industrial process that uses a rotating drum of activated charcoal to burn the organic components of waste water for energy instead of treating it as sewage. It was pointing out that activated charcoal is charcoal that has had its surface area increased (I read about how this is done right here in the SDMB) to something on the order of 5 million square feet per pound. If that is the case, why doesn’t it spontaneously burst into flame?

Thanks for your help,

Because it’s not wet, or because it loses heat too fast?
I’ve little idea, but this staff report might help:
Will charcoal self-ignite if wet?