Yes, there is two ways to carbonate in a keg, Forced and Natural. The natural way is to use 1/2 the amount of priming sugar that you would use for bottling and adding it to a keg and then using pressure to seal it and allowing natural carbonation to occur over a 2 or 3 week period. I have only tried this one time and was disappointed with the outcome. It does seem to result in a higher amount of sludge at the bottom of the keg that needs to be drained off before your pours clear. All of my forced carbed kegs are always crystal clear so I don't do the natural method .