The EM-1 is Spyder based, so I would guess it could run on co2 if you really had to, but really if I were you I wouldn't. No electronic marker with the two exceptions of the Shocker and Impulse is well suited for co2 use because of the problems of co2 freezing and fouling that occurs in firing rapidly, and electros are designed for rapid fire to be common. I would reconsider getting the EM-1 to begin with, getting an Impulse instead if you know you're going to be restricted to co2 for a while, among other very good reasons. Do you see many people that aren't given one for free using an EM-1? Didn't think so. Either buy something commonly used with co2 (stock Cocker, Palmer Blazer, Shocker or Impulse), or save the money for nitro. Compromises with expensive toys of any variety are nearly always a very bad idea.
Nitrogen and compressed air are the same when referred to in the context of paintball.
