Methods Of Drying Coffee Beans


Process of drying

There are two methods for drying coffee beans.

The first is to sun dry the beans. This is natural and the most ecological. The negative is the amount of space required and is subject to varying weather conditions. The second method is mechanical drying. This requires less space and time to dry the beans and is not subject to weather conditions.

Sun Drying


This method achieves the highest quality and flavor for the coffee, and is the method Eco Delight Coffee prefers. A square meter of sun dry beans will yield 100 pounds of parchment beans. To dry the beans in the sun a drying system is required.

Open air clay tile drying patios (photo at right) are constructed and coffee beans are placed on the tiles to dry. As the beans sun dry any moisture under the beans absorb into the tiles enabling the beans to fully dry. Manual or mechanical aeration, turning the beans, is required to dry homogenously and prevent fermentation which will damage the beans.

The African Bed is a wood frame stretcher with a  suspended netting holding the beans above the ground outside in the open. The stretcher allows air circulation above and below the beans.

Both the clay tile patio and African Bed require manpower to constantly rotate the beans in an effort to achieve an even and uniform drying. The main disadvantage of these systems is that they are dependent on weather conditions. Moisture  from dew or rain can hinder the drying process and can damage the quality due to mildew. Creating a green house by placing plastics over the drying patio or African Beds prevents weather moisture from affecting the beans.

Natural coffees, such as some that are used by Eco Delight Coffee are sun dried with the pulp.  This requires careful aeration and heat from the sun to dry uniformly and prevent possible fermentation that damages the beans.


Machine Drying


An alternative to sun drying is to machine dry. Machine drying has the benefit of requiring less space for drying and is not dependent on the weather. Machine drying is ideal for wet climates areas.

The first step in machine drying coffee is to use the Oreadora, shown at left. The Oreadora is a dehumidifier which will remove between 3 – 5% of the moisture from the beans.

The most popular coffee dryer is a rotator drum dryer or Guardiola. The horizontal rotating drum allows a constant warm air flow around the beans eliminating the moisture. The most popular sizes will hold between 700 pounds to 12,000 pounds of beans, which normally require 24 hours to dry. A biomass furnace is used as a heat source.


Dryers Furnaces Heat Source

In  place of using firewood as a heat source for the furnace, a new biomass furnace (shown at right) is used. The husk or parchment is used as the biomass fuel as well as the wood that is obtained from the pruning of the coffee trees and the shade trees. Fresh air is passed through series of ducts and interchanges until it is indirectly heated to the desired temperature. The hot air is then injected into the beans to eliminate the moisture. Indirect heating is very import to drying coffee as direct flame can damage the coffee beans reducing the quality of the coffee.

Now the coffee is ready for dry milling.

Here we are!