All:
There is a HUGE difference in various CO2 QVL's (Quality Verification Levels - there are five).
ISBT (International Society of Beverage Technologists) has CO2 Guidelines for quality - this is what you want. Also CGA G-6.2 QVL I is Beverage Grade CO2 equivalent to ISBT.
"Food Grade" is QVL H. It is technically not Food Grade, it is Food Processing Grade.
Beverage Grade/Quality (ISBT/CGA G-6.2 QVL I) mandates many more impurities be removed that are not even checked in QVL H such as:
Benzene (yes BENZENE), ammonia, phosphine, much lower levels of sulfur and acetaldehyde both of which will affect taste, oil and grease and methanol.
You don't want higher levels of sulfur and acetaldahyde and you sure don't want unchecked benzene levels.