Talking about decaf sometimes reminds me of the old comedy routine about spaghetti growing on trees. Almost any story can sound plausible if you don't have the basic information.
All decaffeination processes --
- start with ordinary green coffee beans,
- are done in large industrial plants, and
- use a solvent that is supposed to dissolve only caffeine and leave the stuff that makes coffee taste good.
The important difference among decaf processes is in which "solvent" is used to dissolve the caffeine. Chemical solvents, most often methylene chloride (MC), are both effective and cheap. The problem is not that there is a residue left in the coffee -- MC is highly volatile even at room temp, and remember that coffee is roasted at over 400F -- but rather that there are environmental hazards associated with using toxic substances such as MC on a large scale.
Using water as the solvent solves the environment problem, but water dissolves not only the caffeine but also other, desirable components in the bean, so there's a loss of flavor. There are ways to mitigate this loss. The Swiss Water™ company has developed (and patented) one such method, as well as a highly effective marketing campaign.
In the best of all worlds we would use a method in which liquefied carbon dioxide (CO2) is the solvent. This process was developed in the 1970's by the German company Hermsen and is still done only in their plants in Bremen. Not only does CO2 decaf taste better, but, from a roasters viewpoint, it's easier to roast well because it behaves more like regular green coffee. For the moment, we're using a water process from Royal Coffee, who at least select really good coffees to decaffeinate.