When kegging you usually carbonate under pressure. No sugar needed. I carb in the keg under about 20 lbs of CO2 pressure. It lowers cost as well. But you need a gas regulator and carbon dioxide tanks, those are expensive...You can buy a lot of carbing sugar for the prices of those items. I got my tanks off of Craig's list, so that helped. Gas regulators are about $60. You need two of them...one to dispense the beer and leave it to your dispensing system, and one on a small CO2 tank to help clean, purge, sanitized tanks and lines. Otherwise you will need to remove your dispensing regulator all the stinkin' time.