The use of water as the solvent to decaffeinate coffee was originally developed in Switzerland in the 1980s and is now used commercially under the trade-mark “Swiss Water Process” by The Swiss Water Decaffeinated Coffee Company of Burnaby, British Columbia, Canada.
They describe it as a “chemical free” process. Green coffee beans can be immersed in water to extract their caffeine but this will also extract desirable oils and other solids from the bean resulting in less flavourful brewed coffee. The Swiss Water process method attempts to overcome this difficulty by using water saturated with these desirable coffee components thus reducing or eliminating their extraction during the decaffeination process.
Water saturated in this way is referred to as green coffee extract or GCE. It is created using a separate batch of green coffee beans that are immersed in water and then discarded. The GCE is then filtered to remove only the caffeine from it. A fresh batch of green coffee beans, are then immersed in the GCE to remove caffeine but retain other components. The process of filtering the GCE to remove caffeine and immersing the beans is repeated until the beans are 99.9% caffeine free by mass. This process takes 8 to 10 hours.