The best replacement for c02 is compressed air.

The best alternatives to c02 are rated as following:
★★★★★  compressed air
★★★★  green gas
★  co2
★  nitrogen
★  pcp
★  co
  c60
  c02

Your alternative for c02 is not listed? Suggest!
Speaking about c02, one probably shouldn't forget about dry ice.

Other search terms related to c02 and their ratings are:
★★★★★ dry ice
You have in mind a companion for c02 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of c02 in all years. Click on graph for more.
c02
compressed air
green gas