Second , the carbon dioxide - rich gas is pressurized and refrigerated until it liquefies .
Such gases can be a byproduct of another process , such as producing ammonia from nitrogen and natural gas , oil refinery activities or large - scale fermentation .
The carbon dioxide - rich gas is pressurized and refrigerated until it liquefies .
Such gases can be a byproduct of another process , such as producing ammonia from nitrogen and natural gas , oil refinery activities or large - scale fermentation .