There are two methods of drying coffee beans.
Sun is natural and most ecological
Machine drying has the benefit of requiring less space for drying and is not dependent on the weather.
There are two methods for drying coffee beans.
The first process is to dry coffee beans from the heat of the sun. This is natural and the most ecological. The negative from this process is the amount of space required and is subject to the varying weather conditions.
The second process is mechanical or machine drying. This process requires less space and time to dry the coffee beans and is not subject to weather conditions.
This method achieves the highest quality and flavor for the coffee beans. This is the method 828 Coffee prefers. A square meter of beans dried in the sun will yield 100 pounds of parchment coffee beans.
To dry the coffee beans in the sun requires a drying system. Open-air clay tile drying patios are constructed and coffee beans are placed on the tiles to dry. As the beans dry under the heat of the sun, any moisture under the beans will absorb into the clay tiles enabling the coffee beans to fully dry. Manual or mechanical aeration, turning the coffee beans, is required to dry homogenously and prevent fermentation, which will damage the beans.
Another example of drying coffee beans in the sun is the African Bed, which is a wood frame stretcher with suspended netting holding the coffee beans above the ground outside in the open. The stretcher allows for air circulation above and below the coffee beans.
Both the the clay tile patio and African Bed require manpower to constantly rotate the coffee beans in an effort to achieve an even and uniform drying process. The main disadvantage of these processes is that they are dependent on the weather conditions. Moisture from dew or rain can hinder the drying process and can damage the quality of the coffee beans due to mildew. Creating a greenhouse by placing plastic over the drying patio or African Bed prevents weather moisture from affecting the coffee beans. 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 climate areas.
The first step in machine drying coffee beans is to use an Oreadora. The Oreadora is a de-humidifier, which will remove between 3-5% of moisture form the coffee beans. The coffee beans are now put into a dryer. The most popular type coffee bean dryer is a rotator drum or Guardiola. The horizontal rotating drum allows a constant warm airflow around the beans eliminating moisture.
The most popular sizes will hold between 700 pounds to 12,000 pounds of coffee beans, which normally require 24 hours to dry. A biomass furnace is used as a heat source. The husk or parchment is used as the biomass fuel primary fuel source. Firewood can be added as a secondary source. Fresh air is passed through a series of ducts and interchanges until it is indirectly heated to the desired temperature. The hot air is then injected into the coffee beans to eliminate the moisture. Indirect heating is very important to drying coffee as direct heat can damage the coffee beans reducing the flavor and quality of the coffee beans.
Now the coffee beans are ready for Dry Milling.