Once coffee is fermented and washed, it must be dried from
46% humidity down to 11%, at which point it is stable to be stored for long
period of time. If this drying doesn’t begin within hours of washing, the high
humidity levels can cause the coffee to develop off flavors and ruin it. At the
beneficio, we will be using solar dryers for this drying process.
When people hear the words “solar dryers” they often think
of solar panels, moving parts, or engines; however, solar dryers use the sun’s
energy in a much more direct way. Solar dryers look much like small
greenhouses, with shelves inside of them to dry coffee. They provide protection
from wind and rain, while concentrating the sun’s energy into a force to dry
the coffee.
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| Solar dryers concentrate the sun's energy to dry coffee |
Other than solar dryers, there are two main forms of coffee
dryers. The highest volume form is mechanical dryers, which load approximately
22,000 lb of coffee into an elevator system and heat coffee by burning wood or
coffee shells. The other is patio drying, in which coffee is spread into thin
layers on a cement patio.
There are two reasons that we are using solar dryers instead
of these other two options: quality and environmental sustainability.
We are configuring our solar dryers to dry coffee in 7-10
days, as opposed to the 4-6 days of patios or the 24 hours of mechanical
dryers. High temperatures created by contact with hot cement or passing near
the flames of mechanical dryers are damaging to the structure of the coffee
bean, lowering the quality. Additionally, coffee is never placed on the ground
using our solar dryers. Patios, which must be used for a short amount of time
even when mechanically drying coffee, are frequent hosts to trucks, children,
dogs, chickens, pigs, and anything else that may be in the area. Finally, there
is no way to bring coffee that is on a patio under shelter quickly in the case
of a rain storm, and rewetting coffee even slightly can completely ruin the
quality. Mechanical dryers cause great physical stress on the coffee—not only
because of high temperatures but also because of the large impacts that happen
as the coffee falls almost 40 feet from the top of the dryer to the bottom.
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Patio drying coffee takes large amounts of space
and dries coffee on the ground, where it is often walked on and driven over |
Our second reason for using solar dryers is that they are an
important part of making an environmentally sustainable beneficio. Drying
patios require extremely large amounts of space and, therefore, a very large
amount of cement. Due to the large area necessary, drying patios also represent
a reduction in arable land. By installing solar dryers, we are keeping the land
surrounding the beneficio available to grow off-harvest plants (from new coffee
seedlings to nitrogen fixing beans to hardwood trees to plant in farms).
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Mechanical dryers have a tall column (blue in picture) with
large furnaces to heat coffee (silver in picture) |
Mechanical dryers, on the other hand take up a relatively
small amount of space but require large amounts of energy input. First, they
require electrical energy to consistently move the 22,000 lb of coffee inside them.
Second, they require large fires to create the temperatures necessary to dry
coffee. This requires the use of wood, causing deforestation; or coffee shells,
which could otherwise be used to make organic fertilizers; and the burning of
either of these produces carbon dioxide which is then released into the
atmosphere. Once built, solar dryers require no input other than one person to
move coffees every 30 minutes.
We installed our first of four solar dryers in a joint
training session with IHCAFE, UMF clients, and members of the COCAQUIL Coffee
Cooperative. The other three will be installed in coming weeks as we prepare to
ramp up processing at the beneficio.
So there you have it—solar dryers.
