well here in IL battery is described this way:
720 ILCS 5/12-3 Battery
(a) A person commits batery if he intentionally or knowingly without legal justification and by any means, (1) causes bodily harm to an individual or (2) makes physical contact of an insulting or provoking nature with an individual
I would say by letter of the law one could say that if a person stepped towards the officer then attempted to pass gas on him it would be physical contact of an insulting or provoking nauture. Knowing the person is an officer only enhances the penalty
So yes I would say if the prosecuting attorney has the kahonies to charge it, then it may fit the letter of the law. Is it a good idea to do so? I can't say, I was not the one that was there and don't know what the details are and I'm sure there is much much more to this story/report than what has been said in the news.
If nothing else it serves the guy right for showing such rude disrespect.