Posted by Arbor Teas on November 29, 2008
This month, we're very excited to announce the replacement of our previous water-process decaffeinated teas with our new CO2 decaffeinated offerings. But many of our enviro-conscious customers may be wondering why we're so excited about using CO2 for anything related to our generally Earth-friendly little tea company. Don't we go to great lengths to eliminate or offset the emission of CO2 from our business? Well here's a bit of background to explain why CO2 isn't so bad for decaffeinating tea.
How CO2 Decaffeination Works
CO2 is a non-toxic, nonflammable, colorless and odorless gas which is a naturally-occurring part of the air we breathe. Although elevated levels of CO2 in our atmosphere contribute to global warming, it's generally a pretty inert substance. Under pressure and temperature, however, CO2 is able to flow freely through natural materials (like tea) and has strong solvent capabilities. This is called its "supercritical" state (which is why CO2 decaffeination is also referred to as "supercritial CO2 decaffeination" or "supercritical fluid extraction," but this is a blog for tea drinkers, not chemists...).
To begin the CO2 decaffeination process, the tea leaves are moistened and placed under pressure. Then streams of pressurized and heated CO2 are passed through the tea leaves, where it dissolves the caffeine while leaving the tea leaves otherwise intact. After passing through the tea leaves, the caffeine-laden CO2 is filtered to remove the caffeine, and then recycled for further use in decaffeination. Finally, the newly-decaffeinated tea leaves are dried.
How CO2 Decaffeination Stacks Up to Other Methods
In addition to CO2 decaffeination, two other methods are used for decaffeinating tea: ethyl acetate and water process. In both cases, the tea leaves are bathed in either of these substances, which dissolve and remove the caffeine. Unfortunately, both of these approaches have drawbacks which make them inferior to CO2 decaffeination. In the case of ethyl acetate, traces of this organic compound (not the good kind of "organic," mind you) can be left behind on the tea, which is generally felt to be unhealthy for human consumption. Water process, on the other hand, is absolutely healthy, but essentially amounts to a pre-infusion of the tea leaves, in which a portion of the desireable compounds in the tea (that contribute flavor, aroma, etc.) are removed with the caffeine.
Is CO2 Decaffeination Safe for the Environment?
In a nutshell, yes. Because the CO2 used for decaffeination is filtered and recycled at a rate of around 99%, very little CO2 is emitted into the atmosphere.