What Are The Merits of Different Green Coffee Processing Methods? I've noticed that there's a distinct lack of Q&amp;A's on green coffee processing methods. As this is one of the earliest steps on the journey from seed to cup, I was curious:

What are the merits of different green coffee processing methods? (i.e., impact on characteristics of coffee, labor, time, etc.)

In other words: Why does Farmer A prefer to use the dry process method while Farmer B favors the wet process?

Processing Methods:


Dry Process
Wet Process
Semi-Dry Process/Pulped Natural
Dry Process | This is the oldest method of modern processing.  It requires very little equipment.  It is basically a manual process of letting the coffee cherries raisin up, then peeling them.  It is a labor intensive process.  Dry processing tends to produce body heavy, smooth coffees with complex notes.  Dry processing is used extensively in Brazil and accounts for the distinct different flavor profiles from other South American coffees.  Dry processing is not practical in humid, wet, or temperate areas, as dry heat is necessary to dry the fruit in a short enough amount of time and to assure that mold or fungus does not set in.
Wet Process | This method start with running the cherries through machinery to remove the skin and outer layers of the fruit.  The beans with remaining inner layers of fruit are soaked in water and allowed to ferment.  Additional processing is done  to remove the final inner layers surrounding the bean.  The result is left to dry (usually with additional machine assistance).  Wet processing requires a comparatively large investment in equipment, access to enough water for the process and creates waste water that must also be dealt with.  The process does allow for multiple areas to sort beans (floating during fermentation, in channel after fruit strip, etc) that potentially allow for a more uniform product.  Wet processed coffees tend to be missing the overt fruit notes of a dry process, but this is debatable and can vary based on fermentation methods (additional additives are sometimes used in the fermenting process).  
Semi-Dry / Pulped Natural / Wet Hulled / Semi-Washed | This process is similar to the wet process except the fermentation step is skipped and specialized machines are used to strip the final layers from around the bean.  This method can produce beans with the best of both processing methods, but the machines used to strip the inner layers away are also prone to damaging beans.  This is a faster method of processing but again requires machine investment and resource use.  


There are many other factors influencing coffee processing that should be kept in mind.  Individual farmers may not have a choice of processing method.  In many places the processing centers for coffee are quite separate from farms and only one processing center may be available.  Local conditions will also largely dictate what methods are appropriate or available.  There are also a myriad of variations on these methods that may produce different results and weather can play a factor as well (think about an area hit by a monsoon while large batches are trying to dry).  At some level, all farmers are trying to get paid for what they produce.  That being the case, most will prefer some combination of whatever local processing method is available and/or cheapest and produces the highest pricing for their product.