Is it possible to decaffeinate regular coffee beans at home? If so, what method works best?
The short answer is: no, I don't think it's possible. Perhaps you could use some household chemicals to leech out the caffeine, but I'm fairly certain you won't want to use what remains to make coffee.
Wow, I wasn't looking for a WAG. I checked further to answer my own question, and will share the following, from coffeesearch.org/science. Short answer - don't try this at home, kids.
Coffee Decaffeination Process
Decaffeinating coffee is achieved through a variety of decaffeination processes, all of which are relatively harmless to your health, but harmful to coffee quality. Almost every process for decaffeination consists of soaking the beans in water to dissolve the caffeine, extracting the caffeine with either a solvent or activated carbon, and then re-soaking the coffee beans in the decaffeinated water to reabsorb the flavor compounds that were lost in the initial extraction. The solvents typically used are methylene chloride or ethyl acetate, which both have a low boiling point. Since ethyl acetate is found naturally in fruits you will hear people call this process "natural." In any case the solvent never comes in contact with the coffee bean itself, but only the water solution containing the caffeine that was previously extracted from the coffee bean. Therefore the water decaffeination process is relatively benign. All methods used to decaffeinate coffee are based on equilibrium principles and solvent/solute properties. As such, neither all of the caffeine is removed from the coffee, nor are all of the flavor compounds returned or left in the coffee. The chemical composition of decaffeinated coffee (or decaf coffee) is altered, and therefore the flavor and aroma are changed.
How to Decaffeinate Coffee
Swiss Water Process
In the Swiss Water Process, the green coffee beans are soaked in hot water to remove the caffeine and compounds responsible for much of the flavor of the coffee flavor. The first batch of coffee beans is then discarded, while the caffeine is stripped from the solution by means of activated carbon filters. This leaves a solution saturated with flavor compounds, which is then used to soak a new batch of decaffeinated green coffee beans. The principle of water procesed decaf coffee is that the solution is saturated with all components soluble in water other than caffeine. Therefore, only the caffeine in the bean is allowed to escape whereas the rest of the compounds are in equilibrium. Unfortunately, the flavor of batches is intermixed since the chemically saturated solution is used repeatedly.
In the carbon dioxide decaffeination process, green coffee beans are soaked in highly compressed CO2, which extracts the caffeine. The caffeine is then removed from the CO2 using activated carbon filters, which are then reused to extract caffeine from the coffee again.
Sparkling Water Process
The sparkling water decaffeination process is similar to the CO2 method, but instead of removing the caffeine with activated carbon filters, the caffeine is washed from the CO2 with sparkling water in a secondary tank, which is then recycled to extract more caffeine from the coffee. The solvent consists of approximately 99.7% compressed carbon dioxide and 0.3% water.